Interview › Databases & Caching
What is AWS DMS, and when would you use it?
Databases & Caching · Intermediate level
Answer
AWS DMS is a managed migration and replication service that can perform full loads and change data capture between supported sources and targets. I use it for cloud migrations, heterogeneous migrations, and low-downtime moves when native replication is not ideal.
Technical explanation
WAL/binlog volume affects storage, backup, replica lag, and restore behavior.
Near-zero downtime migration requires initial load, CDC, validation, short write drain, cutover, and rollback planning.
DMS helps move data, but schema conversion, application compatibility, and data validation remain engineering responsibilities.
Hands-on example
Migration runbook:
1. Create target database and schema.
2. Start full-load plus CDC using DMS or logical replication.
3. Monitor lag and task errors.
4. Compare row counts and critical aggregates.
5. Stop writes briefly.
6. Wait for lag to reach zero.
7. Switch endpoint/secret.
8. Monitor app errors and DB load.
9. Keep source read-only until rollback window closes.
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