Online migration to Amazon Keyspaces: strategies and best practices

Application dual-writes: You can implement dual writes in your application using existing Cassandra client libraries and drivers. Designate one database as the leader and the other as the follower. Write failures to the follower database are recorded in a dead letter queue (DLQ) for analysis.

Messaging tier dual-writes: Alternatively, you can configure your existing messaging platform to send writes to both Cassandra and Amazon Keyspaces using an additional consumer. This creates eventually consistent views across both databases.

Copy historical data: You can migrate historical data from Cassandra to Amazon Keyspaces using Amazon Glue or custom extract, transform, and load (ETL) scripts. Handle conflict resolution between dual writes and bulk loads using techniques like lightweight transactions or timestamps.

Use Time-To-Live (TTL): For shorter data retention periods, you can use TTL in both Cassandra and Amazon Keyspaces to avoid uploading unnecessary historical data. As old data expires in Cassandra and new data is written via dual-writes, Amazon Keyspaces eventually catches up.

Dual reads: Implement dual reads from both Cassandra (primary) and Amazon Keyspaces (secondary) databases, comparing results asynchronously. Differences are logged or sent to a DLQ.

Sample reads: Use Λ functions to periodically sample and compare data across both systems, logging any discrepancies to a DLQ.

Blue-green strategy: Switch your application to treat Amazon Keyspaces as the primary and Cassandra as the secondary data store in a single step. Monitor performance and roll back if issues arise.

Canary deployment: Gradually roll out the migration to a subset of users first, incrementally increasing traffic to Amazon Keyspaces as the primary until fully migrated.