Neptune provides two ways of implementing cross-region failover capabilities:
Cross-region snapshot copy and restore
Using Neptune streams to replicate data between two clusters in two different regions.
Cross-region snapshot copy and restore has the lowest operational overhead for recovering a Neptune cluster in a different region. However, copying a snapshot between regions can requires significant data-transfer time, since a snapshot is a full backup of the Neptune cluster. As a result, cross-region snapshot copy and restore can be used for scenarios that only require a Recovery Point Objective (RPO) of hours and a Recovery Time Objective (RTO) of hours.
A Recovery Point Objective (RPO) is measured by the time in between backups. It defines how much data may be lost between the time the last backup was made and the time at which the database is recovered.
A Recovery Time Objective (RTO) is measured by the time it takes to perform a recovery operation. This is the time it takes the DB cluster to fail over to a recovered database after a failure occurs.
Neptune streams provides a way to keep a backup Neptune cluster in sync with the primary production cluster at all times. If a failure occurs, your database then fails over to the backup cluster. This reduces RPO and RTO to minutes, since data is constantly being copied to the backup cluster, which is immediately available as a failover target at any time.
The drawback of using Neptune streams in this way is that both the operational overhead required to maintain the replication components, and the cost of having a second Neptune DB cluster online all of the time, can be significant.
