The company needs the application in the secondary Region to operate independently from the primary Region during disaster recovery. That means both the DynamoDB data and the relational customer data must be present and usable in the secondary Region without cross-Region dependencies at runtime. The company also wants the least development effort, which usually means using native managed replication features rather than building custom replication logic.
For DynamoDB, global tables are the managed multi-Region, multi-active replication feature. Global tables replicate changes between Regions automatically and allow applications in each Region to read and write to local DynamoDB tables, removing dependencies on the primary Region.
For the RDS for MySQL database, the straightforward managed approach for cross-Region disaster recovery with minimal development change is to create a cross-Region read replica in the secondary Region. A read replica uses asynchronous replication to keep data up to date. During a disaster recovery event, the company can promote the read replica in the secondary Region to become a standalone primary database instance. This provides a simple, low-development approach for having the data in the secondary Region. The application in the secondary Region can be configured to use the replica endpoint in normal times and can continue operating with the promoted instance during failover.
Option A combines DynamoDB global tables with an RDS read replica in the secondary Region. This is the least development effort because it uses AWS-managed replication for both data stores and requires only configuration changes and endpoint selection in the secondary application.
Option B is not correct because DAX is a caching layer for DynamoDB, not a replication or disaster recovery mechanism. DAX does not replicate DynamoDB tables into another Region and cannot replace having the DynamoDB data present in the secondary Region.
Option C is incorrect because RDS Multi-AZ is a high availability feature within a single Region, using synchronous replication to a standby in another Availability Zone. Multi-AZ does not create a standby in a different Region, and it does not provide cross-Region DR by itself.
Option D is less desirable because it requires custom development and operations: processing DynamoDB streams, building and operating a replication pipeline, and ensuring correctness and ordering across Regions. This is higher development effort than enabling DynamoDB global tables.
Therefore, using DynamoDB global tables plus an RDS read replica in the secondary Region (option A) meets the DR independence requirement with the least development effort.
[References:AWS documentation on DynamoDB global tables for multi-Region replication with local read/write access in each Region.AWS documentation on Amazon RDS for MySQL cross-Region read replicas and promoting a read replica for disaster recovery., , ]
