Alternative to the blue green deployment in Opensearch

Yes, it is now possible to make certain changes to your Amazon OpenSearch Service cluster without going through a blue/green deployment. This includes updating the EBS volume size, volume type, IOPS, throughput, and in some cases, the number of data nodes.

For EBS volume changes: You can now update the cluster volume size, volume type, IOPS, and throughput without requiring a blue/green deployment. This feature is available for OpenSearch Service domains with current generation instances and when the volume size per data node is within 3 TiB. However, decreasing storage volume size or making storage volume changes within short intervals will still require a blue/green deployment.

For data node count changes: Amazon OpenSearch Service now allows you to update the number of data nodes without a blue/green deployment in two scenarios:

1. For clusters with dedicated cluster manager (master) nodes
2. For clusters without dedicated cluster manager nodes, running any OpenSearch version or Elasticsearch versions 7.1 and above

It's important to note that if you modify both the data node instance type and count simultaneously, OpenSearch Service will still use a blue/green deployment.

These updates allow for faster changes with minimal disruption to your cluster operations and online traffic. You can use the dry-run option to check whether your specific change requires a blue/green deployment.

These improvements make it easier to manage your OpenSearch clusters and adapt to changing requirements without the need for extensive planning during low-traffic periods, as was previously recommended for blue/green deployments.
Sources
Amazon OpenSearch Service now lets you update cluster volume without blue/green
Amazon OpenSearch Service now lets you update node count without blue/green
Community | AWS open source newsletter, #189
Community | AWS open source newsletter, #195