Which solution meets these requirements with the LEAST amount of operational effort?
Enable cluster mode in ElastiCache for Redis. Then create multiple clusters across Regions and replicate the cache data by using AWS Database Migration Service (AWS DMS). Promote a cluster in the failover Region to handle production traffic when DR is required.
Create a global datastore in ElastiCache for Redis. Then create replica clusters in two other Regions. Promote one of the replica clusters as primary when DR is required.
Disable cluster mode in ElastiCache for Redis. Then create multiple replication groups across Regions and replicate the cache data by using AWS Database Migration Service (AWS DMS). Promote a replication group in the failover Region to primary when DR is required.
Create a snapshot of ElastiCache for Redis in the primary Region and copy it to the failover Region. Use the snapshot to restore the cluster from the failover Region when DR is required.
Explanations:
AWS Database Migration Service (DMS) is not designed for Redis replication and does not support low-latency replication for cache data. This approach adds unnecessary complexity.
A Global Datastore in ElastiCache for Redis provides cross-Region replication with low-latency, built-in failover, and encryption. This solution meets the DR and security requirements.
AWS DMS is not suitable for replicating Redis data. Additionally, replication groups in Redis are designed for scaling within a single region, not across Regions for DR.
Snapshot-based restore is not ideal for disaster recovery in a global context, as it involves manual intervention and does not support low-latency or real-time failover.
I conclude that the answer is:
Create a global datastore in ElastiCache for Redis. Then create replica clusters in two other Regions. Promote one of the replica clusters as primary when DR is required.