Fault tolerance

Checks if your Application Load Balancers are configured to use more than one Availability Zone (AZ). An AZ is a distinct location that is insulated from failures in other zones. Configure your load balancer in multiple AZs in the same Region to help improve your workload availability.

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Yellow: ALB is in a single AZ.

Green: ALB has two or more AZs.

Make sure that your load balancer is configured with at least two Availability Zones.

For more information, see Availability Zones for your Application Load Balancer.

For more information, see the following documentation:

Checks if an Amazon Aurora MySQL cluster has backtracking enabled.

Amazon Aurora MySQL cluster backtracking is a feature that allows you to restore an Aurora DB cluster to a previous point in time without creating a new cluster. It enables you to roll back your database to a specific point in time within a retention period, without the need to restore from a snapshot.

You can adjust the backtracking time window (hours) in the BacktrackWindowInHours parameter of the AWS Config rules.

For more information, see Backtracking an Aurora DB cluster.

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AWS Config Managed Rule: aurora-mysql-backtracking-enabled

Yellow: Amazon Aurora MySQL clusters backtracking is not enabled.

Turn on backtracking for your Amazon Aurora MySQL cluster.

For more information, see Backtracking an Aurora DB cluster.

Backtracking an Aurora DB cluster

Checks for cases where an Amazon Aurora DB cluster has both private and public instances.

When your primary instance fails, a replica can be promoted to a primary instance. If that replica is private, users who have only public access would no longer be able to connect to the database after failover. We recommend that all the DB instances in a cluster have the same accessibility.

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Yellow: The instances in an Aurora DB cluster have different accessibility (a mix of public and private).

Modify the Publicly Accessible setting of the instances in the DB cluster so that they are all either public or private. For details, see the instructions for MySQL instances at Modifying a DB Instance Running the MySQL Database Engine.

Fault Tolerance for an Aurora DB Cluster

Checks that an origin group is configured for distributions that include two origins in Amazon CloudFront.

For more information, see Optimizing high availability with CloudFront origin failover.

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AWS Config Managed Rule: cloudfront-origin-failover-enabled

Yellow: Amazon CloudFront origin failover is not enabled.

Make sure that you turn on the origin failover feature for your CloudFront distributions to help ensure high availability of your content delivery to end users. When you turn on this feature, traffic is automatically routed to the backup origin server if the primary origin server is unavailable. This minimizes potential downtime and ensures continuous availability of your content.

Checks the AWS Key Management Service (AWS KMS) key permissions for an endpoint where the underlying model was encrypted by using customer managed keys. If the customer managed key is disabled, or the key policy was changed to alter the allowed permissions for Amazon Comprehend, the endpoint availability might be affected.

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Red: The customer managed key is disabled or the key policy was changed to alter the allowed permissions for Amazon Comprehend access.

If the customer managed key was disabled, we recommend that you enable it. For more information, see Enabling keys. If the key policy was altered and you want to keep using the endpoint, we recommend that you update the AWS KMS key policy. For more information, see Changing a key policy.

AWS KMS Permissions

Checks if there are Amazon DocumentDB clusters configured as Single-AZ.

Running Amazon DocumentDB workloads in a Single-AZ architecture is not sufficient for highly critical workloads and it can take up to 10 minutes to recover from a component failure. Customers should deploy replica instances in additional availability zones to ensure availability during maintenance, instance failures, component failures, or availability zone failures.

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Yellow: Amazon DocumentDB cluster has instances in less than three availability zones.

Green: Amazon DocumentDB cluster has instances in three availability zones.

If your application requires high availability, modify your DB instance to enable Multi-AZ using replica instances. See Amazon DocumentDB High Availability and Replication

Understanding Amazon DocumentDB Cluster Fault Tolerance

Regions and Availability Zones

Checks if point-in time-recovery is enabled for your Amazon DynamoDB tables.

Point-in time-recovery helps protect your DynamoDB tables from accidental write or delete operations. With point-in time-recovery, you don't have to worry about creating, maintaining, or scheduling on-demand backups. Point-in time-recovery restores tables to any point in time during the last 35 days. DynamoDB maintains incremental backups of your table.

For more information, see Point-in-time recovery for DynamoDB.

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AWS Config Managed Rule: dynamodb-pitr-enabled

Yellow: Point-in-time recovery is not enabled for your DynamoDB tables.

Turn on point-in-time recovery in Amazon DynamoDB to continuously back up your table data.

For more information, see Point-in-time recovery: How it works.

Point-in-time recovery for DynamoDB

Checks if Amazon DynamoDB tables are part of an AWS Backup plan.

AWS Backup provides incremental backups for DynamoDB tables that capture changes made since the last backup. Including DynamoDB tables in an AWS Backup plan helps protect your data from accidental data loss scenarios and automates the backup process. This provides a reliable and scalable backup solution for your DynamoDB tables, helping to ensure that your valuable data is protected and available for recovery as needed.

For more information, see Creating backups of DynamoDB tables with AWS Backup

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AWS Config Managed Rule: dynamodb-in-backup-plan

Yellow: Amazon DynamoDB table is not included in AWS Backup plan.

Ensure that your Amazon DynamoDB tables are part of an AWS Backup plan.

Scheduled backups

What is AWS Backup?

Creating backup plans using the AWS Backup console

Checks if Amazon EBS volumes are present in backup plans for AWS Backup.

Include Amazon EBS volumes in an AWS Backup plan to automate regular backups for the data stored on those volumes. This protects you against data loss, makes data management easier, and allows for data restoration when needed. A backup plan helps to ensure that your data is safe and that you're able to meet recovery time and point objectives (RTO/RPO) for your application and services.

For more information, see Creating a backup plan

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AWS Config Managed Rule: ebs-in-backup-plan

Yellow: Amazon EBS volume is not included in AWS Backup plan.

Make sure that your Amazon EBS volumes are part of an AWS Backup plan.

Creating backup plans using the AWS Backup console

What is AWS Backup?

Getting started 3: Create a scheduled backup

Checks the age of the snapshots for your Amazon EBS volumes (either available or in-use). Failures can occur even if Amazon EBS volumes are replicated. Snapshots are persisted toAmazon S3 for durable storage and point-in-time recovery.

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Create weekly or monthly snapshots of your volumes. For more information, see Creating an Amazon EBS Snapshot.

To automate the creation of EBS snapshots, you can consider using AWS Backup or Amazon Data Lifecycle Manager.

Amazon Elastic Block Store (Amazon EBS)

Amazon EBS Snapshots

AWS Backup

Amazon Data Lifecycle Manager

Checks if your Amazon EC2 Auto Scaling groups that are associated with a Classic Load Balancer are using Elastic Load Balancing health checks. The default health checks for an Auto Scaling group are Amazon EC2 status checks only. If an instance fails these status checks, it is marked unhealthy and is terminated. Amazon EC2 Auto Scaling launches a new replacement instance. The Elastic Load Balancing health check periodically monitors Amazon EC2 instances to detect and terminate unhealthy instances and then launch new instances.

For more information, see Add Elastic Load Balancing health checks.

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AWS Config Managed Rule: autoscaling-group-elb-healthcheck-required

Yellow: Amazon EC2 Auto Scaling group attached to Classic Load Balancer has not enabled Elastic Load Balancing health checks.

Ensure that your Auto Scaling groups that are associated with a Classic Load Balancer use Elastic Load Balancing health checks.

Elastic Load Balancing health checks report if the load balancer is healthy and available to handle requests. This ensures high availability for your application.

For more information, see Add Elastic Load Balancing health checks to an Auto Scaling group

Checks if Capacity Rebalancing is enabled for Amazon EC2 Auto Scaling groups that use multiple instance types.

Configuring Amazon EC2 Auto Scaling groups with capacity rebalancing helps ensure that Amazon EC2 instances are evenly distributed across Availability Zones, regardless of instance types and purchasing options. It uses a target tracking policy associated with the group, such as CPU utilization or network traffic.

For more information, see Auto Scaling groups with multiple instance types and purchase options.

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AWS Config Managed Rule: autoscaling-capacity-rebalancing

Yellow: Amazon EC2 Auto Scaling group capacity rebalancing is not enabled.

Ensure that capacity rebalancing is enabled for your Amazon EC2 Auto Scaling groups that use multiple instance types.

For more information, see Enable Capacity Rebalancing (console)

Checks if the Amazon EC2 Auto Scaling group is deployed in multiple Availability Zones, or the minimum number of Availability Zones specified. Deploy Amazon EC2 instances in multiple Availability Zones to ensure high availability.

You can adjust the minimum number of Availability Zones using the minAvailibilityZones parameter in your AWS Config rules.

For more information, see Auto Scaling groups with multiple instance types and purchase options.

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AWS Config Managed Rule: autoscaling-multiple-az

Red: The Amazon EC2 Auto Scaling group doesn't have multiple AZs configured, or doesn't meet the minimum number of AZs specified.

Make sure that your Amazon EC2 Auto Scaling group is configured with multiple AZs. Deploy Amazon EC2 instances in multiple Availability Zones to ensure high availability.

Create an Auto Scaling group using a launch template

Create an Auto Scaling group using a launch configuration

Checks the distribution of Amazon Elastic Compute Cloud (Amazon EC2) instances across Availability Zones in a Region.

Availability Zones are distinct locations that are insulated from failures in other Availability Zones. This allows inexpensive, low-latency network connectivity between Availability Zones in the same Region. By launching instances in multiple Availability Zones in the same Region, you can help protect your applications from a single point of failure.

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Balance your Amazon EC2 instances evenly across multiple Availability Zones. You can do this by launching instances manually or by using Auto Scaling to do it automatically. For more information, see Launch Your Instance and Load Balance Your Auto Scaling Group.

Checks if detailed monitoring is enabled for yourAmazon EC2 instances.

Amazon EC2 detailed monitoring provides more frequent metrics, published at one-minute intervals, instead of the five-minute intervals used in Amazon EC2 basic monitoring. Enabling detailed monitoring for Amazon EC2 helps you better manage your Amazon EC2 resources, so that you can find trends and take action faster.

For more information, see Basic monitoring and detailed monitoring.

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AWS Config Managed Rule: ec2-instance-detailed-monitoring-enabled

Yellow: Detailed monitoring is not enabled for Amazon EC2 instances.

Turn on detailed monitoring for your Amazon EC2 instances to increase the frequency at which Amazon EC2 metric data is published to Amazon CloudWatch (from 5-minute to 1-minute intervals).

Checks for Amazon ECS task definitions configured with the AWSLogs logging driver in blocking mode. A driver configured in the blocking mode risks system availability.

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Yellow: The awslogs driver logging configuration parameter mode is set to blocking or missing. A missing mode parameter indicates a default blocking configurations.

Green: Amazon ECS task definition is not using the awslogs driver or the awslogs driver is configured in non-blocking mode.

To mitigate the availability risk, consider changing the task definition AWSLogs driver configuration from blocking to non-blocking. With non-blocking mode, you will have to set a value for the max-buffer-size parameter. For more information and guidance on configuration parameters, see . See Preventing log loss with non-blocking mode in the AWSLogs container log driver

Using the AWS logs log driver

Choosing container logging options to avoid backpressure

Preventing log loss with non-blocking mode in the AWSLogs container log driver

Checks that your service configuration uses a single Availability Zone (AZ).

An AZ is a distinct location that is insulated from failures in other zones. This supports inexpensive, low-latency network connectivity between AZs in the same AWS Region. By launching instances in multiple AZs in the same Region, you can help protect your applications from a single point of failure.

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Create at least one more task for the service in a different AZ.

Amazon ECS capacity and availability

Checks that your Amazon ECS service uses the spread placement strategy based on Availability Zone (AZ). This strategy distributes tasks across Availability Zones in the same AWS Region and can help protect your applications from a single point of failure.

For tasks that run as part of an Amazon ECS service, spread is the default task placement strategy.

This check also verifies that spread is the first or only strategy in your list of enabled placement strategies.

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Enable the spread task placement strategy to distribute tasks across multiple AZs. Verify that spread by availability zone is the first strategy for all enabled task placement strategies or the only strategy used. If you choose to manage AZ placement, you can use a mirrored service in another AZ to mitigate these risks.

Amazon ECS task placement strategies

Checks if mount targets exist in multiple Availability Zones for an Amazon EFS file system.

An Availability Zone is a distinct location that is insulated from failures in other zones. By creating mount targets in multiple geographically separated Availability Zones within an AWS Region, you can achieve the highest levels of availability and durability for your Amazon EFS file systems.

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For EFS file systems using One Zone storage classes, we recommend you create new file systems that use Standard storage classes by restoring a backup to a new file system. Then create mount targets in multiple Availability Zones.

For EFS file systems using Standard storage classes, we recommend you create mount targets in multiple Availability Zones.

Checks if Amazon EFS file systems are included in backup plans with AWS Backup.

AWS Backup is a unified backup service designed to simplify the creation, migration, restoration, and deletion of backups, while providing improved reporting and auditing.

For more information, see Backing up your Amazon EFS file systems.

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AWS Config Managed Rule: EFS_IN_BACKUP_PLAN

Red: Amazon EFS are not included in AWS Backup plan.

Make sure that your Amazon EFS file systems are included in your AWS Backup plan to protect against accidental data loss or data corruption.

Backing up your Amazon EFS file systems

Amazon EFS Backup and Restore using AWS Backup.

Checks for ElastiCache clusters that deploy in a single Availability Zone (AZ). This check alerts you if Multi-AZ is inactive in a cluster.

Deployments in multiple AZs enhance ElastiCache cluster availability by asynchronously replicating to read-only replicas in a different AZ. When planned cluster maintenance occurs, or a primary node is unavailable, ElastiCache automatically promotes a replica to primary. This failover allows cluster write operations to resume, and doesn't require an administrator to intervene.

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Create at least one replica per shard, in an AZ that is different than the primary.

For more information, see Minimizing downtime in ElastiCache (Redis OSS) with Multi-AZ.

Checks if the Amazon ElastiCache (Redis OSS) clusters have automatic backup turned on and if the snapshot retention period is above the specified or 15 day default limit. When automatic backups are enabled, ElastiCache creates a backup of the cluster on a daily basis.

You can specify your desired snapshot retention limit using the snapshotRetentionPeriod parameters of your AWS Config rules.

For more information, see Backup and restore for ElastiCache (Redis OSS).

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AWS Config Managed Rule: elasticache-redis-cluster-automatic-backup-check

Red: Amazon ElastiCache (Redis OSS) clusters do not have automatic backup turned on or the snapshot retention period is below the limit.

Make sure that Amazon ElastiCache (Redis OSS) clusters have automatic backup turned on and the snapshot retention period is above the specified or 15 day default limit. Automatic backups can help guard against data loss. In the event of a failure, you can create a new cluster, restoring your data from the most recent backup.

For more information, see Backup and restore for ElastiCache (Redis OSS).

For more information, see Scheduling automatic backups.

Checks for MemoryDB clusters that deploy in a single Availability Zone (AZ). This check alerts you if Multi-AZ is inactive in a cluster.

Deployments in multiple AZs enhance MemoryDB cluster availability by asynchronously replicating to read-only replicas in a different AZ. When planned cluster maintenance occurs, or a primary node is unavailable, MemoryDB automatically promotes a replica to primary. This failover allows cluster write operations to resume, and doesn't require an administrator to intervene.

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Create at least one replica per shard, in an AZ that is different than the primary.

For more information, see Minimizing downtime in MemoryDB with Multi-AZ.

Checks that the brokers of a Managed Streaming for Kafka (MSK) Cluster do not have more than the recommended number of partitions assigned.

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Follow the MSK recommended best practices to scale your MSK Cluster or delete any unused partitions.

Checks the number of Availability Zones (AZs) for your Amazon MSK provisioned cluster. The Amazon MSK cluster is formed of several brokers that work together and distribute the data and load. Production might be interrupted during maintenance or broker issues in a 2-AZ cluster.

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To increase availability of the cluster, you can create another cluster in a 3 AZs setup. Then migrate the existing cluster to the new cluster that you created. You can use Amazon MSK replication for this migration.

Amazon MSK high availability

Amazon MSK migration

Checks if Amazon OpenSearch Service domains are configured with at least three data nodes and ZoneAwarenessEnabled is true. With ZoneAwarenessEnabled enabled, Amazon OpenSearch Service ensures that each primary shard and its corresponding replica are allocated in different Availability Zones.

For more information, see Configuring a multi-AZ domain in Amazon OpenSearch Service.

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AWS Config Managed Rule: opensearch-data-node-fault-tolerance

Yellow: Amazon OpenSearch Service domains are configured with less than three data nodes.

Make sure that Amazon OpenSearch Service domains are configured with a minimum of three data nodes. Configure a multi-AZ domain to enhance the availability of the Amazon OpenSearch Service cluster by allocating nodes and replicating data across three Availability Zones within the same Region. This prevents data loss and minimizes downtime in the event of node or data center (AZ) failure.

For more information, see Increase availability for Amazon OpenSearch Service by deploying in three Availability Zones.

Checks for automated backups of Amazon RDS DB instances.

By default, backups are enabled with a retention period of one day. Backups reduce the risk of unexpected data loss and allow for point-in-time recovery.

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Red: A DB instance has the backup retention period set to 0 days.

Set the retention period for the automated DB instance backup to 1 to 35 days as appropriate to the requirements of your application. See Working With Automated Backups.

Getting Started with Amazon RDS

Checks if an Amazon RDS instance is enabled with automated backups using Amazon RDS or with continuous backups of AWS Backup. Continuous backups reduce the risk of unexpected data loss and allow for point-in-time recovery.

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Make sure that Amazon RDS instances have automated backup configured either by setting a retention period greater than 0 in Amazon RDS or by creating a continuous backup plan using AWS Backup.

Add at least another DB instance to the DB cluster to improve availability and performance.

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Yellow: DB clusters have only one DB instance.

Add a reader DB instance to the DB cluster.

In the current configuration, one DB instance is used for both read and write operations. You can add another DB instance to allow read redistribution and a failover option.

For more information, see High availability for Amazon Aurora.

The DB clusters are currently in a single Availability Zone. Use multiple Availability Zones to improve the availability.

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Yellow: DB clusters have all the instances in the same Availability Zone.

Add the DB instances to multiple Availability Zones in your DB cluster.

We recommend that you add the DB instances to multiple Availability Zones in a DB cluster. Adding DB instances to multiple Availability Zones improvesthe availability of your DB cluster.

For more information, see High availability for Amazon Aurora.

Your DB cluster has all the reader instances in the same Availability Zone. We recommend that you distribute the Reader instances across multiple Availability Zones in your DB cluster.

Distribution increases the availability of the database, and improves the response time by reducing network latency between clients and the database.

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Red: DB clusters have the reader instances in the same Availability Zone.

Distribute the reader instances across multiple Availability Zones.

Availability Zones (AZs) are locations that are distinct from each other to provide isolation in case of outages within each AWS Region. We recommend that you distribute the primary instance and reader instances in your DB cluster across multiple AZs to improve the availability of your DB cluster. You can create a Multi-AZ cluster using the AWS Management Console, AWS CLI, or Amazon RDS API when you create the cluster. You can modify the existing Aurora cluster to a Multi-AZ cluster by adding a new reader instance and specifying a different AZ.

For more information, see High availability for Amazon Aurora.

Checks if your Amazon RDS DB instances have Enhanced Monitoring enabled.

Amazon RDS Enhanced Monitoring provides metrics in real time for the operating system (OS) that your DB instance runs on. All system metrics and process information for your Amazon RDS DB instances can be view on the Amazon RDS console. And, you can customize the dashboard. With Enhanced Monitoring, you have visibility of your Amazon RDS instance operation status in near real time, allowing you to respond to operational issues faster.

You can specify your desired monitoring interval using the monitoringInterval parameter of your AWS Config rules.

For more information, see Overview of Enhanced Monitoring and OS metrics in Enhanced Monitoring.

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AWS Config Managed Rule: rds-enhanced-monitoring-enabled

Yellow: Your Amazon RDS DB instances don't have Enhanced Monitoring enabled or are not configured with the desired interval.

Enable Enhanced Monitoring for your Amazon RDS DB instances to improve the visibility of your Amazon RDS instance operation status.

For more information, see Monitoring OS metrics with Enhanced Monitoring.

OS metrics in Enhanced Monitoring

Amazon RDS storage autoscaling isn't turned on for your DB instance. When there is an increase in the database workload, RDS Storage autoscaling automatically scales the storage capacity with zero downtime.

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Red: DB instances don't have storage autoscaling turned on.

Turn on Amazon RDS storage autoscaling with a specified maximum storage threshold.

Amazon RDS storage autoscaling automatically scales storage capacity with zero downtime when the database workload increases. Storage autoscaling monitors the storage usage and automatically scales up the capacity when the usage is close to the provisioned storage capacity. You can specify a maximum limit on the storage that Amazon RDS can allocate to the DB instance. There is no additional cost for storage autoscaling. You pay only for the Amazon RDS resources that are allocated to your DB instance. We recommend that you turn on Amazon RDS storage autoscaling.

For more information, see Managing capacity automatically with Amazon RDS storage autoscaling.

We recommend that you use Multi-AZ deployment. The Multi-AZ deployments enhance the availability and durability of the DB instance.

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Yellow: DB instances aren't using Multi-AZ deployment.

Set up Multi-AZ for the impacted DB instances.

In an Amazon RDS Multi-AZ deployment, Amazon RDS automatically creates a primary database instance and replicates the data to an instance in a different availability zone. When it detects a failure, Amazon RDS automatically fails over to a standby instance without manual intervention.

For more information, see Pricing.

Checks to see if the CloudWatch metric DiskQueueDepth shows that number of queued writes to the RDS Instance database storage has grown to a level where an operational investigation should be suggested.

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Consider moving to instances and storage volumes that support the read/write characteristics.

Checks to see if the FreeStorageSpace CloudWatch metric for an RDS database instance has decreased below an operationally reasonable threshold.

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Scale up the storage space for the RDS database instance that is running low on free storage using the Amazon RDS Management Console, Amazon RDS API or AWS Command Line Interface.

When log_output is set to TABLE, more storage is used than when log_output is set to FILE. We recommend that you set the parameter to FILE, to avoid reaching the storage size limit.

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Yellow: DB parameter groups have log_output parameter set to TABLE.

Set the log_output parameter value to FILE in your DB parameter groups.

For more information, see MySQL database log files.

Your DB instance encounters a known issue: A table created in a MySQL version lower than 8.0.26 with the row_format set to COMPACT or REDUNDANT is inaccessible and unrecoverable when the index exceeds 767 bytes.

We recommend that you set the innodb_default_row_format parameter value to DYNAMIC.

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Red: DB parameter groups have an unsafe setting for the innodb_default_row_format parameter.

Set the innodb_default_row_format parameter to DYNAMIC.

When a table is created with MySQL version lower than 8.0.26 with row_format set to COMPACT or REDUNDANT, creating indexes with a key prefix shorter than 767 bytes isn't enforced. After the database restarts, these tables can't be accessed or recovered.

For more information, see Changes in MySQL 8.0.26 (2021-07-20, General Availability)n on the MySQL documentation website.

The value of the innodb_flush_log_at_trx_commit parameter of your DB instance isn't a safe value. This parameter controls the persistence of commit operations to disk.

We recommend that you set the innodb_flush_log_at_trx_commit parameter to 1.

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Yellow: DB parameter groups have innodb_flush_log_at_trx_commit set to other than 1.

Set the innodb_flush_log_at_trx_commit parameter value to 1

The database transaction is durable when the log buffer is saved to the durable storage. However, saving to the disk impacts performance. Depending on the value set for innodb_flush_log_at_trx_commit parameter, the behavior of how logs are written and saved to the disk can vary.

For more information, see Best practices for configuring parameters for Amazon RDS for MySQL, part 1: Parameters related to performance.

Your DB instance has a low value for the maximum number of simultaneous connections for each database account.

We recommend setting the max_user_connections parameter to a number greater than 5.

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Yellow: DB parameter groups have max_user_connections misconfigured.

Increase the value of the max_user_connections parameter to a number greater than 5.

The max_user_connections setting controls the maximum number of simultaneous connections allowed for a MySQL user account. Reaching this connection limit cause failures in the Amazon RDS instance administration operations, such as backup, patching, and parameters changes.

For more information, see Setting Account Resource Limits on the MySQL documentation website.

Checks for DB instances that are deployed in a single Availability Zone (AZ).

Multi-AZ deployments enhance database availability by synchronously replicating to a standby instance in a different Availability Zone. During planned database maintenance, or the failure of a DB instance or Availability Zone, Amazon RDS automatically fails over to the standby. This failover allows database operations to resume quickly without administrative intervention. Because Amazon RDS does not support Multi-AZ deployment for Microsoft SQL Server, this check does not examine SQL Server instances.

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Yellow: A DB instance is deployed in a single Availability Zone.

If your application requires high availability, modify your DB instance to enable Multi-AZ deployment. See High Availability (Multi-AZ).

Regions and Availability Zones

Checks if your Amazon RDS DB instances are included in a backup plan in AWS Backup.

AWS Backup is a fully managed backup service that makes it easy to centralize and automate backing up data across AWS services.

Including your Amazon RDS DB instance in a backup plan is important for regulatory compliance obligations, disaster recovery, business policies for data protection, and business continuity goals.

For more information, see What is AWS Backup?.

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AWS Config Managed Rule: rds-in-backup-plan

Yellow: An Amazon RDS DB instance is not included in a backup plan with AWS Backup.

Include your Amazon RDS DB instances in a backup plan with AWS Backup.

For more information, see Amazon RDS Backup and Restore Using AWS Backup.

Assigning resources to a backup plan

Your DB instance has a read replica in writable mode, which allows updates from clients.

We recommend that you set the the read_only parameter to TrueIfReplica so that the read replicas isn't in writable mode.

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Yellow: DB parameter groups turn on writable mode for the read replicas.

Set the read_only parameter value to TrueIfReplica.

The read_only parameter controls the write permission from the clients to a database instance. The default value for this parameter is TrueIfReplica. For a replica instance, TrueIfReplica sets the read_only value to ON (1) and disables any write activity from the clients. For a master/writer instance, TrueIfReplica sets the value to OFF (0) and enables the write activity from the clients for the instance. When the read replica is opened in writable mode, the data stored in this instance may diverge from the primary instance which causes replication errors.

For more information, see Best practices for configuring parameters for Amazon RDS for MySQL, part 2: Parameters related to replication on the MySQL documentation website.

Automated backups are disabled on your DB resources. Automated backups enable point-in-time recovery of your DB instance.

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Red: Amazon RDS resources don't have automated backups turned on

Turn on automated backups with a retention period of up to 14 days.

Automated backups enable point-in-time recovery of your DB instances. We recommend turning on automated backups. When you turn on automated backups for a DB instance, Amazon RDS automatically performs a full backup of your data daily during your preferred backup window. The backup captures transaction logs when there are updates to your DB instance. You get backup storage up to the storage size of your DB instance at no additional cost.

For more information, see the following resources:

The synchronization of the binary log to disk isn't enforced before the transaction commits are acknowledged in your DB instance.

We recommend that you set the sync_binlog parameter value to 1.

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Yellow: DB parameter groups have synchronous binary logging turned off.

Set the sync_binlog parameter to 1.

The sync_binlog parameter controls how MySQL pushes the binary log to disk. When the value of this parameter is set to 1, it turns on binary log synchronization to disk before transactions are committed. When the value of this parameter is set to 0, it turns off the binary log synchronization to the disk. Typically, MySQL server depends on the operating system to push the binary log to disk regularly similar to other files. The sync_binlog parameter value set to 0 can enhance the performance. However, during a power failure or an operating system crash, the server loses all the committed transactions that weren't synchronized to the binary logs.

For more information, see Best practices for configuring parameters for Amazon RDS for MySQL, part 2: Parameters related to replication.

Checks if your Amazon RDS DB clusters have Multi-AZ replication enabled.

A Multi-AZ DB cluster has a writer DB instance and two reader DB instances in three separate Availability Zones. Multi-AZ DB clusters provide high availability, increased capacity for read workloads, and lower latency when compared to Multi-AZ deployments.

For more information, see Creating a Multi-AZ DB cluster.

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AWS Config Managed Rule: rds-cluster-multi-az-enabled

Yellow: Your Amazon RDS DB cluster does not have Multi-AZ replication configured

Turn on Multi-AZ DB cluster deployment when you create an Amazon RDS DB cluster.

For more information, see Creating a Multi-AZ DB cluster.

Multi-AZ DB cluster deployments

Checks if your Amazon RDS DB instances have a Multi-AZ standby replica configured.

Amazon RDS Multi-AZ provides high availability and durabiliy for database instances by replicating data to a standby replica in a different Availability Zone. This provides automatic failover, improve performance, and enhances data durability. In a Multi-AZ DB instance deployment, Amazon RDS automatically provisions and maintains a synchronous standby replica in a different Availability Zone. The primary DB instance is synchronously replicated across Availability Zones to a standby replica to provide data redundancy and minimize latency spikes during system backups. Running a DB instance with high availability enhances availability during planned system maintenance. It can also help protect your databases against DB instance failure and Availability Zone disruption.

For more information, see Multi-AZ DB instance deployments.

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AWS Config Managed Rule: rds-multi-az-support

Yellow: An Amazon RDS DB instance does not have a Multi-AZ replica configured.

Turn on Multi-AZ deployment when you create an Amazon RDS DB instance.

This check can't be excluded from view in the Trusted Advisor console.

Multi-AZ DB instance deployments

Checks to see if the ReplicaLag CloudWatch metric for an RDS database instance has increased above an operationally reasonable threshold over the past week.

ReplicaLag metric measures the number of seconds a read replica is behind the primary instance. Replication lag occurs when the asynchronous updates made to the read replica cannot keep up with the updates happening on the primary database instance. In the event of a failure to the primary instance, data could be missing from the read replica if the ReplicaLag is above an operationally reasonable threshold.

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There are several possible causes for ReplicaLag to increase beyond operationally safe levels. For example, it can be caused by recently replaced/launched replica instances from older backups and these replicas requiring substantial time to “catch-up” to the primary database instance and live transactions. This ReplicaLag may dwindle over time as catch-up occurs. Another example could be that the transaction velocity able to be achieved on the primary database instance is higher than the replication process or replica infrastructure is able to match. This ReplicaLag may grow over time as replication fails to keep pace with the primary database performance. Finally, the workload may be bursty throughout different periods of the day/month/etc. that result in occasional ReplicaLag to fall behind. Your team should investigate which possible root cause has contributed to high ReplicaLag for the database, and possibly change the database instance type or other characteristics of the workload to ensure data continuity on the replica matches your requirements.

When the synchronous_commit parameter is turned off, data can be lost in a database crash. The durability of the database is at risk.

We recommend that you turn on the synchronous_commit parameter.

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Red: DB parameter groups have synchronous_commit parameter turned off.

Turn on synchronous_commit parameter in your DB parameter groups.

The synchronous_commit parameter defines the Write-Ahead Logging (WAL) process completion before the database server sends a successful notification to the client. This commit is called as an asynchronous commit because the client acknowledges the commit before WAL saves the transaction in the disk. If the synchronous_commit parameter is turned off, then the transactions can be lost, DB instance durability might be compromised, and data might be lost when a database crashes.

For more information, see MySQL database log files.

Checks if automated snapshots are enabled for your Amazon Redshift clusters.

Amazon Redshift automatically takes incremental snapshots that track changes to the cluster since the previous automated snapshot. Automated snapshots retain all of the data required to restore a cluster from a snapshot. To disable automated snapshots, set the retention period to zero. You can't disable automated snapshots for RA3 node types.

You can specify your desired minimum and maximum retention period using the MinRetentionPeriod and MaxRetentionPeriod parameter of your AWS Config rules.

Amazon Redshift snapshots and backups

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AWS Config Managed Rule: redshift-backup-enabled

Red: Amazon Redshift does not have automated snapshots configured within the desired retention period.

Make sure that automated snapshots are enabled for your Amazon Redshift clusters.

For more information, see Managing snapshots using the console.

Amazon Redshift snapshots and backups

For more information, see Working with backups.

Checks for resource record sets that are associated with health checks that have been deleted.

Route 53 does not prevent you from deleting a health check that is associated with one or more resource record sets. If you delete a health check without updating the associated resource record sets, the routing of DNS queries for your DNS failover configuration will not work as intended.

Hosted zones created by AWS services won't appear in your check results.

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Yellow: A resource record set is associated with a health check that has been deleted.

Create a new health check and associate it with the resource record set. See Creating, Updating, and Deleting Health Checks and Adding Health Checks to Resource Record Sets.

Checks for Amazon Route 53 failover resource record sets that have a misconfiguration.

When Amazon Route 53 health checks determine that the primary resource is unhealthy, Amazon Route 53 responds to queries with a secondary, backup resource record set. You must create correctly configured primary and secondary resource record sets for failover to work.

Hosted zones created by AWS services won't appear in your check results.

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If a failover resource set is missing, create the corresponding resource record set. See Creating Failover Resource Record Sets.

If your resource record sets are associated with the same health check, create separate health checks for each one. See Creating, Updating, and Deleting Health Checks.

Amazon Route 53 Health Checks and DNS Failover

Checks for resource record sets that can benefit from having a lower time-to-live (TTL) value.

TTL is the number of seconds that a resource record set is cached by DNS resolvers. When you specify a long TTL, DNS resolvers take longer to request updated DNS records, which can cause unnecessary delay in rerouting traffic (for example, when DNS Failover detects and responds to a failure of one of your endpoints). This check looks only at records with a policy of Failover, or if there is an associated health check.

Hosted zones created by AWS services won’t appear in your check results.

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Enter a TTL value of 60 seconds for the listed resource record sets. For more information, see Working with Resource Record Sets.

Amazon Route 53 Health Checks and DNS Failover

Checks for Amazon Route 53 hosted zones for which your domain registrar or DNS is not using the correct Route 53 name servers.

When you create a hosted zone, Route 53 assigns a delegation set of four name servers. The names of these servers are ns-###.awsdns-##.com, .net, .org, and .co.uk, where ### and ## typically represent different numbers. Before Route 53 can route DNS queries for your domain, you must update your registrar's name server configuration to remove the name servers that the registrar assigned. Then, you must add all four name servers in the Route 53 delegation set. For maximum availability, you must add all four Route 53 name servers.

Hosted zones created by AWS services won't appear in your check results.

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Yellow: A hosted zone for which the registrar for your domain does not use all four of the Route 53 name servers in the delegation set.

Add or update name server records with your registrar or with the current DNS service for your domain to include all four of the name servers in your Route 53 delegation set. To find these values, see Getting the Name Servers for a Hosted Zone. For information about adding or updating name server records, see Creating and Migrating Domains and Subdomains to Amazon Route 53.

Working with Hosted Zones

Checks to see if your service configuration has IP addresses specified in at least two Availability Zones (AZs) for redundancy. An AZ is a distinct location that is insulated from failures in other zones. By specifying IP addresses in multiple AZs in the same Region, you can help protect your applications from a single point of failure.

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Specify IP addresses in at least two Availability Zones for redundancy.

Checks the logging configuration of Amazon Simple Storage Service (Amazon S3) buckets.

When server access logging is enabled, detailed access logs are delivered hourly to a bucket that you choose. An access log record contains details about each request, such as the request type, the resources specified in the request, and the time and date the request was processed. By default, bucket logging is not enabled. You should enable logging if you want to perform security audits or learn more about users and usage patterns.

When logging is initially enabled, the configuration is automatically validated. However, future modifications can result in logging failures. This check examines explicit Amazon S3 bucket permissions, but it does not examine associated bucket policies that might override the bucket permissions.

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Enable bucket logging for most buckets. See Enabling Logging Using the Console and Enabling Logging Programmatically.

If the target bucket permissions do not include the root account and you want Trusted Advisor to check the logging status, add the root account as a grantee. See Editing Bucket Permissions.

If the target bucket does not exist, select an existing bucket as a target or create a new one and select it. See Managing Bucket Logging.

If the target and source have different owners, change the target bucket to one that has the same owner as the source bucket. See Managing Bucket Logging.

If the log deliverer does not have write permissions for the target (write not enabled), grant Upload/Delete permissions to the Log Delivery group. See Editing Bucket Permissions.

Checks if your Amazon S3 buckets have replication rules enabled for Cross-Region Replication, Same-Region Replication, or both.

Replication is the automatic, asynchronous copying of objects across buckets in the same or different AWS Regions. Replication copies newly created objects and object updates from a source bucket to a destination bucket or buckets. Use Amazon S3 bucket replication to help improve the resilience and compliance of your applications and data storage.

For more information, see Replicating objects.

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AWS Config Managed Rule: s3-bucket-replication-enabled

Yellow: Amazon S3 bucket replication rules are not enabled for Cross-Region Replication, Same-Region Replication, or both.

Turn on Amazon S3 bucket replication rules to improve the resiliency and compliance of your applications and data storage.

For more information, see View your backup jobs and recovery points and Setting up replication.

Walkthroughs: Examples for configuring replication

Checks for Amazon Simple Storage Service buckets that do not have versioning enabled, or that have versioning suspended.

When versioning is enabled, you can easily recover from both unintended user actions and application failures. Versioning allows you to preserve, retrieve, and restore any version of any object stored in a bucket. You can use lifecycle rules to manage all versions of your objects, as well as their associated costs, by automatically archiving objects to the Glacier storage class. Rules can also be configured to remove versions of your objects after a specified period of time. You can also require multi-factor authentication (MFA) for any object deletions or configuration changes to your buckets.

Versioning can't be deactivated after it has been enabled. However, it can be suspended, which prevents new versions of objects from being created. Using versioning can increase your costs for Amazon S3, because you pay for storage of multiple versions of an object.

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Enable bucket versioning on most buckets to prevent accidental deletion or overwriting. See Using Versioning and Enabling Versioning Programmatically.

If bucket versioning is suspended, consider re-enabling versioning. For information on working with objects in a versioning-suspended bucket, see Managing Objects in a Versioning-Suspended Bucket.

When versioning is enabled or suspended, you can define lifecycle configuration rules to mark certain object versions as expired or to permanently remove unneeded object versions. For more information, see Object Lifecycle Management.

MFA Delete requires additional authentication when the versioning status of the bucket is changed or when versions of an object are deleted. It requires the user to enter credentials and a code from an approved authentication device. For more information, see MFA Delete.

Working with Buckets

Checks If your load balancers (Application, Network, and Gateway Load Balancer) are configured with subnets across multiple Availability Zones.

You can specify your desired minimum Availability Zones in the minAvailabilityZones parameters of your AWS Config rules.

For more information, see Availability Zones for your Application Load Balancer, Availability Zones - Network Load Balancers, and Create a Gateway Load Balancer.

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AWS Config Managed Rule: elbv2-multiple-az

Yellow: Application, Network, or Gateway Load Balancers configured with subnets in less than two Availability Zones.

Configure your Application, Network, and Gateway Load Balancers with subnets across multiple Availability Zones.

Availability Zones for your Application Load Balancer

Availability Zones (Elastic Load Balancing)

Create a Gateway Load Balancer

Checks that sufficient available IPs remain among targeted Subnets.Having sufficient IPs available for use would help when Auto Scaling Group reaches its maximum size and needs to launch additional instances.

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Increase the number of available IP addresses

Examines the health check configuration for Auto Scaling groups.

If Elastic Load Balancing is being used for an Auto Scaling group, the recommended configuration is to enable an Elastic Load Balancing health check. If an Elastic Load Balancing health check is not used, Auto Scaling can only act upon the health of the Amazon Elastic Compute Cloud (Amazon EC2) instance. Auto Scaling will not act on the application running on the instance.

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If the Auto Scaling group has an associated load balancer, but the Elastic Load Balancing health check is not enabled, see Add an Elastic Load Balancing Health Check to your Auto Scaling Group.

If the Elastic Load Balancing health check is enabled, but no load balancer is associated with the Auto Scaling group, see Set Up an Auto-Scaled and Load-Balanced Application.

Amazon EC2 Auto Scaling User Guide

Checks the availability of resources associated with your launch configurations, launch templates, and your Auto Scaling groups.

Auto Scaling groups that point to unavailable resources cannot launch new Amazon Elastic Compute Cloud (Amazon EC2) instances. When properly configured, Auto Scaling causes the number of Amazon EC2 instances to increase seamlessly during demand spikes, and decrease automatically during demand lulls. Auto Scaling groups and launch configurations/launch templates that point to unavailable resources do not operate as intended.

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If the load balancer has been deleted, either create a new load balancer or target group and then associate it to the Auto Scaling group. or create a new Auto Scaling group without the load balancer. For information about creating a new Auto Scaling group with a new load balancer, see Set Up an Auto-Scaled and Load-Balanced Application. For information about creating a new Auto Scaling group without a load balancer, see Create Auto Scaling Group in Getting Started With Auto Scaling Using the Console.

If the AMI has been deleted, then create a new launch configuration or launch template version using a valid AMI and associate it with an Auto Scaling group. For information on how to create a new launch configuration, see Create a launch configuration in the Amazon EC2 Auto Scaling User Guide. For information on how to create a launch template, see Create a launch template for an Auto Scaling group in the Amazon EC2 Auto Scaling User Guide.

If your launch templates include an AWS Systems Manager parameter that include an Amazon Machine Image (AMI) ID , then review the launch template to make sure that the parameters reference a valid AMI ID, or make the appropriate changes in the AWS Systems Manager parameter store. For more information, see Use AWS Systems Manager parameters instead of AMI IDs in the Amazon EC2 Auto Scaling User Guide.

Checks your clusters that run HSM instances in a single Availability Zone (AZ). This check alerts you if your clusters are at risk of not having the most recent backup.

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Create at least one more instance for the cluster in a different Availability Zone.

Best practices for AWS CloudHSM

Checks the resilience of the AWS Direct Connect used to connect your on-premises to each Direct Connect gateway or virtual private gateway.

This check alerts you if any Direct Connect gateway or virtual private gateway isn't configured with virtual interfaces across at least two distinct Direct Connect locations. Lack of location resiliency can result in unexpected downtime during maintenance, a fiber cut, a device failure, or a complete location failure.

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Red: The Direct Connect gateway or virtual private gateway is configured with one or more virtual interfaces on a single Direct Connect device.

Yellow: The Direct Connect gateway or virtual private gateway is configured with virtual interfaces across multiple Direct Connect devices in a single Direct Connect location.

Green: The Direct Connect gateway or virtual private gateway is configured with virtual interfaces across two or more distinct Direct Connect locations.

To build Direct Connect location resiliency, you can configure the Direct Connect gateway or virtual private gateway to connect to at least two distinct Direct Connect locations. For more information, see AWS Direct Connect Resiliency Recommendation.

AWS Direct Connect Resiliency Recommendations

AWS Direct Connect Failover Test

Checks if an AWS Lambda function is configured with a dead-letter queue.

A dead-letter queue is a feature of AWS Lambda that allows you to capture and analyze failed events, providing a way to handle those events accordingly. Your code might raise an exception, time out, or run out of memory, resulting in failed asynchronous executions of your Lambda function. A dead-letter queue stores messages from failed invocations, providing a way to handle the messages and troubleshoot the failures.

You can specify the dead-letter queue resource that you want to check using the dlqArns parameter in your AWS Config rules.

For more information, see Dead-letter queues.

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AWS Config Managed Rule: lambda-dlq-check

Yellow: AWS Lambda function has no dead-letter queue configured.

Make sure that your AWS Lambda functions have a dead-letter queue configured to control message handling for all failed asynchronous invocations.

For more information, see Dead-letter queues.

Checks that Lambda functions in your account have On Failure event destination or Dead Letter Queue (DLQ) configured for asynchronous invocations, so that records from failed invocations can be routed to a destination for further investigation or processing.

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Please set up On Failure event destination or DLQ for your Lambda functions to send failed invocations along with other details to one of the available destination AWS services for further debugging or processing.

Checks the $LATEST version of VPC-enabled Lambda functions that are vulnerable to service interruption in a single Availability Zone. It’s a best practice that VPC-enabled functions are connected to multiple Availability Zones for high availability.

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Yellow: The $LATEST version of a VPC-enabled Lambda function is connected to subnets in a single Availability Zone.

When configuring functions for access to your VPC, choose subnets in multiple Availability Zones to ensure high availability.

Checks for Outposts Racks balance. This evaluates if a customers Outposts instances are deployed across multiple Outposts Racks or to a single Outpost Rack. A single Outposts rack creates a single point of failure for issues that involve a single Rack (for example, environmental failures). These scenarios can be mitigated by deploying outposts across multiple Racks.

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If you are running production workloads on AWS Outposts, then its a best practice to use the following resilient architecture. A single AWS Outposts rack creates a single point of failure. Consider adding a second AWS Outposts rack to that location with enough capacity for a failover event, and then distribute workloads across racks.

Failure mode 4: Racks or data centers

Checks if an Application Component (AppComponent) in your application is unrecoverable. If an AppComponent doesn't recover in the case of a disruption event, you might experience unknown data loss and system downtime.

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Red: AppComponent is unrecoverable.

To ensure that your AppComponent is recoverable, review and implement the resiliency recommendations, and then run a new assessment. For more information about reviewing the resiliency recommendations, see Additional Resources.

Reviewing resiliency recommendations

AWS Resilience Hub concepts

AWS Resilience Hub User Guide

Checks Resilience Hub for applications that don't meet the recovery time objective (RTO) and recovery point objective (RPO) that the policy defines. The check alerts you if your application doesn't meet the RTO and RPO objectives you've set for an application in Resilience Hub.

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Sign in to the Resilience Hub console and review the recommendations so that your application meets the RTO and RPO objectives.

Resilience Hub concepts

Checks if you have run an assessment for your applications in Resilience Hub. This check alerts you if your resilience scores are below a specific value.

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Sign in to the Resilience Hub console and run an assessment for your application. Review the recommendations to improve the resilience score.

Resilience Hub concepts

Checks how long since you last ran an application assessment. This check alerts you if you haven’t run an application assessment for a specified number of days.

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Sign in to the Resilience Hub console and run an assessment for your application.

Resilience Hub concepts

Checks the number of tunnels that are active for each of your AWS Site-to-Site VPNs.

A VPN should have two tunnels configured at all times. This provides redundancy in case of outage or planned maintenance of the devices at the AWS endpoint. For some hardware, only one tunnel is active at a time. If a VPN has no active tunnels, charges for the VPN might still apply.

For more information, see What is AWS Site-to-Site VPN?

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AWS Config Managed Rule: vpc-vpn-2-tunnels-up

Yellow: A Site-to-Site VPN has at least one tunnel DOWN.

Make sure that two tunnels are configured for VPN connections. And, if your hardware supports it, then make sure that both tunnels are active. If you no longer need a VPN connection, then delete it to avoid charges.

For more information, see Your customer gateway device and the content available on the AWS Knowledge Center.

Checks for high risk issues (HRIs) for your workloads in the reliability pillar. This check is based on your AWS-Well Architected reviews. Your check results depend on whether you completed the workload evaluation with AWS Well-Architected.

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AWS Well-Architected detected high risk issues during your workload evaluation. These issues present opportunities to reduce risk and save money. Sign in to the AWS Well-Architected tool to review your answers and take action to resolve your active issues.

Checks if Classic Load Balancer spans multiple Availability Zones (AZs).

A load balancer distributes incoming application traffic across multiple Amazon EC2 instances in multiple Availability Zones. By default, the load balancer distributes traffic evenly across the Availability Zones that you enable for your load balancer. If one Availability Zone experiences an outage, then load balancer nodes automatically forward requests to the healthy registered instances in one or more Availability Zones.

You can adjust the minimum number of Availability Zones using the minAvailabilityZones parameter in your AWS Config rules

For more information, see What is a Classic Load Balancer?.

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AWS Config Managed Rule: clb-multiple-az

Yellow: Classic Load Balancer does not have Multi-AZ configured or does not meet the minimum number of AZs specified.

Make sure that your Classic Load Balancers have multiple Availability Zones configured. Span your load balancer across multiple AZs to make sure that you have high availability of your application.

For more information, see Tutorial: Create a Classic Load Balancer.

Checks for Classic load balancers that do not have connection draining enabled.

When connection draining is not enabled and you deregister an Amazon EC2 instance from a Classic load balancer, the Classic load balancer stops routing traffic to that instance and closes the connection. When connection draining is enabled, the Classic load balancer stops sending new requests to the deregistered instance but keeps the connection open to serve active requests.

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Enable connection draining for the Classic load balancer. For more information, see Connection Draining and Enable or Disable Connection Draining for Your Load Balancer.

Elastic Load Balancing Concepts

Checks the target groups’ target distribution across Availability Zones (AZs) for Application Load Balancer (ALB), Network Load Balancer (NLB), and Gateway Load Balancer (GWLB).

This check excludes the following:

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For better resilience, make sure that your targets groups have same number of targets across AZs.

Target groups for your Application Load Balancers

Register targets with your Application Load Balancer target group

Checks if your Gateway Load Balancer (GWLB) endpoints are configured as route destination from another Availability Zone (AZ).

Gateway Load Balancer endpoints forward network traffic to firewall appliances behind a Gateway Load Balancer for inspection. Each Gateway Load Balancer endpoint operates within a designated AZ and is built with redundancy in only that AZ. So any resources in a particular AZ must use a Gateway Load Balancer endpoint in the same AZ. This makes sure that any potential outage of a Gateway Load Balancer endpoint or its AZ doesn’t impact your resources in another AZ.

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Check the AZ of your subnet and configure its route table to route traffic through a Gateway Load Balancer endpoint in the same AZ.

If there is no Gateway Load Balancer endpoint in the AZ, then create a new one and then route your subnet traffic through it.

If you have the same route table associated across subnets in different AZs, then keep this route table associated to the subnets that reside in the same AZ as the Gateway Load Balancer endpoint. For subnets in the other AZ, you can then associate a separate route table with a route to a Gateway Load Balancer endpoint in the this AZ.

It’s a best practice to choose a maintenance window for architecture changes in your Amazon VPC.

Checks your load balancer configuration.

To help increase the level of fault tolerance in Amazon Elastic Compute Cloud (Amazon EC2) when using Elastic Load Balancing , we recommend running an equal number of instances across multiple Availability Zones in a Region. A load balancer that is configured accrues charges, so this is a cost-optimization check as well.

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Ensure that your load balancer points to active and healthy instances in at least two Availability Zones. For more information, see Add Availability Zone.

If your load balancer is configured for an Availability Zone with no healthy instances, or if there is an imbalance of instances across the Availability Zones, determine if all the Availability Zones are necessary. Omit any unnecessary Availability Zones and ensure there is a balanced distribution of instances across the remaining Availability Zones. For more information, see Remove Availability Zone.

Checks if your NAT Gateways are configured with Availability Zone (AZ) independence.

A NAT Gateway enables resources in your private subnet to securely connect to services outside the subnet using the NAT Gateway’s IP addresses and drops any unsolicited inbound traffic. Each NAT Gateway operates within a designated Availability Zone (AZ) and is built with redundancy in that AZ only. Therefore, your resources in a particular AZ should use a NAT Gateway in the same AZ so that any potential outage of a NAT Gateway or its AZ does not impact your resources in another AZ.

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Please check the AZ of your subnet and route traffic through a NAT Gateway in the same AZ.

If there is no NATGW in the AZ, please create one and then route your subnet traffic through it.

If you have the same route table associated across subnets in different AZs, keep this route table associated to the subnets that reside in the same AZ as the NAT Gateway and for subnets in the other AZ, please associate a separate route table with a route to a NAT Gateway in this other AZ.

We recommend choosing a maintenance window for architecture changes in your Amazon VPC.

Checks if your AWS Network Firewall endpoints are configured as a route destination from another Availability Zone (AZ).

Network Firewall endpoints forward network traffic to a Network Firewall for inspection. Each Network Firewall endpoint operates within a designated AZ and is built with redundancy only in that AZ. Your resources in a particular AZ should use a Network Firewall endpoint in the same AZ. This makes sure that any potential outage of a Network Firewall endpoint or its AZ doesn’t impact your resources in another AZ. Network traffic that originates in a different AZ for traffic inspection incurs cross-AZ data transfer charges. It’s a best practice to make sure that all resources in a specific AZ use a Network Firewall in the same AZ to avoid cross-AZ data charges.

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Check the AZ of your subnet and route traffic through a Network Firewall endpoint in the same AZ.

If there is no Network Firewall endpoint in the AZ, then create a new Network Firewall and route your subnet traffic through it.

If the same route table is associated across multiple subnets in different AZs, then keep this route table associated to the subnets that reside in the same AZ as the Network Firewall endpoint. For subnets in other AZs, associate a separate route table with a route to a Network Firewall endpoint in that AZ.

It’s a best practice to choose a maintenance window for architecture changes in your Amazon VPC.

Data Transfer within the same AWS Region

Understanding data transfer charges

Availability Zone Independence

High Level steps for implementing a firewall

Creating a firewall

AWS Well-Architected Tool - Use bulkhead architectures to limit scope of impact

Checks if your Network Firewalls are configured to use more than one Availability Zone (AZ) for firewall endpoints.

An AZ is a distinct location that’s insulated from failures in other zones. If the Network Firewall endpoint is deployed in only 1 AZ, then it can be a single point of failure and can impair workloads from other AZs using the Network Firewall for traffic inspection. It’s a best practice to configure your Network Firewalls in multiple AZs in the same Region to mprove your workload availability.

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Make sure that your Network Firewall is configured with at least two AZs for production workloads.

VPC subnet configuration forAWS Network Firewall

Creating a firewall

Availability Zone

AWS Well-Architected Tool - Deploy the workload to multiple locations

Appliance in a shared services VPC

Checks if cross-zone load balancing is enabled on Network Load Balancers.

Cross-zone load balancing helps maintain even distribution of incoming traffic across instances in different Availability Zones. This prevents the load balancer from routing all traffic to instances in the same Availability Zone, which can cause uneven traffic distribution and potential overloading. The feature also helps application reliability by automatically routing traffic to healthy instances in other Availability Zones in the event of a single Availability Zone failure.

For more information, see Cross-zone load balancing.

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AWS Config Managed Rule: nlb-cross-zone-load-balancing-enabled

Ensure that cross-zone load balancing is enabled on Network Load Balancers.

Cross-zone load balancing (Network Load Balancers)

Checks if an internet-facing Network Load Balancer (NLB) is configured with a private subnet. An internet-facing Network Load Balancer (NLB) must be configured in public subnets in order to receive traffic. A public subnet is defined as a subnet that has a direct route to an internet gateway. If the subnet is configured as private, then it’s Availability Zone (AZ) doesn’t receive traffic, which can cause availability issues.

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Red: NLB is configured with one or more private subnets

Green: No private subnet is configured for internet-facing NLB

Confirm that the subnets configured in an internet-facing load balancer are public. A public subnet is defined as a subnet that has a direct route to an internet gateway. Use one of following options:

Checks if your Network Load Balancers are configured to use more than one Availability Zone (AZ). An AZ is a distinct location that is insulated from failures in other zones. Configure your load balancer in multiple AZs in the same Region to help improve your workload availability.

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Yellow: NLB is in a single AZ.

Green: NLB has two or more AZs.

Make sure that your load balancer is configured with at least two Availability Zones.

For more information, see the following documentation:

Checks that an Incident Manager replication set’s configuration uses more than one AWS Region to support regional failover and response. For incidents created by CloudWatch alarms or EventBridge events, Incident Manager creates an incident in the same AWS Region as the alarm or event rule. If Incident Manager is temporarily unavailable in that Region, the system attempts to create an incident in another Region in the replication set. If the replication set includes only one Region, the system fails to create an incident record while Incident Manager is unavailable.

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Add at least one more Region to the replication set.

For more information, see Cross-region Incident management.

Checks through network patterns if your egress network traffic is routing through a single Availability Zone (AZ).

An AZ is a distinct location that is insulated from any impact in other zones. By spreading your service across multiple AZs, you limit the blast radius of an AZ failure.

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If your application requires high availability, consider implementing a multi-AZ architecture for higher availability.

Checks if your AWS PrivateLink VPC interface endpoints are configured to use more than one Availability Zone (AZ). An AZ is a distinct location that is insulated from failures in other zones. This supports inexpensive, low-latency network connectivity between AZs in the same AWS Region. Select subnets in multiple AZs when you create interface endpoints to help protect your applications from a single point of failure.

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Yellow: VPC endpoint is in a single AZ.

Green: VPC endpoint is in at least two AZs.

Make sure that your VPC interface endpoint is configured with at least two Availability Zones.

For more information, see the following documentation:

Checks the number of tunnels that are active for each of your Site-to-Site VPNs.

A VPN should have two tunnels configured at all times. This provides redundancy in case of outage or planned maintenance of the devices at the AWS endpoint. For some hardware, only one tunnel is active at a time. If a VPN has no active tunnels, charges for the VPN might still apply. For more information, see AWS Site-to-Site VPN User Guide.

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Be sure that two tunnels are configured for your VPN connection, and that both are active if your hardware supports it. If you no longer need a VPN connection, you can delete it to avoid charges. For more information, see Your customer gateway device or Delete a Site-to-Site VPN connection.

Checks that Amazon MQ for ActiveMQ brokers are configured for high availability with an active/standby broker in multiple Availability Zones.

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Create a new broker with active/standby deployment mode.

Checks that Amazon MQ for RabbitMQ brokers are configured for high availability with cluster instances in multiple Availability Zones.

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Create a new broker with the cluster deployment mode.