What is Multi-AZ in RDS, and how does failover work?
AWS · Intermediate level
Answer
RDS Multi-AZ is primarily high availability. RDS maintains a standby in another AZ and fails over the endpoint during infrastructure failure or maintenance, so applications must handle brief reconnects and retries.
Technical explanation
Applications must reconnect through the RDS endpoint after failover and should avoid long DNS caching.
Database service choice depends on data model, access patterns, consistency requirements, operational burden, scaling model, and failure tolerance.
Managed databases still require customer ownership of schema, indexes, queries, IAM/network security, backups, upgrades, and restore validation.
Production data design should include encryption, private networking, least-privilege access, monitoring, backups, failover testing, and cost controls.
Hands-on example
1. Create the database/cache in private subnets with encryption, least-privilege security groups, backup/retention settings, and monitoring enabled.
2. Run a representative workload test and capture latency, throughput, connection count, CPU, memory, I/O, and errors.
3. Test the failure path: failover, replica lag, cache loss, throttling, or restore depending on the service.
4. Write the operational runbook covering access, backup, scaling, alarms, and rollback.
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