The AWS SDK for JavaScript v2 has reached end-of-support. We recommend that you migrate to [AWS SDK for JavaScript v3](https://docs.aws.amazon.com//sdk-for-javascript/v3/developer-guide/). For additional details and information on how to migrate, please refer to this [announcement](https://aws.amazon.com/blogs//developer/announcing-end-of-support-for-aws-sdk-for-javascript-v2/).

# Reusing Connections with Keep-Alive in Node.js
<a name="node-reusing-connections"></a>

By default, the default Node.js HTTP/HTTPS agent creates a new TCP connection for every new request. To avoid the cost of establishing a new connection, you can reuse an existing connection.

For short-lived operations, such as DynamoDB queries, the latency overhead of setting up a TCP connection might be greater than the operation itself. Additionally, since DynamoDB [encryption at rest](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/encryption.howitworks.html) is integrated with [AWS KMS](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/encryption.howitworks.html), you may experience latencies from the database having to re-establish new AWS KMS cache entries for each operation.

The easiest way to configure SDK for JavaScript to reuse TCP connections is to set the ` AWS_NODEJS_CONNECTION_REUSE_ENABLED` environment variable to `1`. This feature was added in the [2.463.0](https://github.com/aws/aws-sdk-js/blob/master/CHANGELOG.md#24630) release.

Alternatively, you can set the `keepAlive` property of an HTTP or HTTPS agent set to `true`, as shown in the following example.

```
const AWS = require('aws-sdk');
// http or https
const http = require('http');
const agent = new http.Agent({
  keepAlive: true, 
// Infinity is read as 50 sockets
  maxSockets: Infinity
});

AWS.config.update({
  httpOptions: {
    agent
  }
});
```

The following example shows how to set `keepAlive` for just a DynamoDB client:

```
const AWS = require('aws-sdk')
// http or https
const https = require('https');
const agent = new https.Agent({
  keepAlive: true
});

const dynamodb = new AWS.DynamoDB({
  httpOptions: {
    agent
  }
});
```

If `keepAlive` is enabled, you can also set the initial delay for TCP Keep-Alive packets with `keepAliveMsecs`, which by default is 1000ms. See the [Node.js documentation](https://nodejs.org/api/http.html) for details.