Interview › Databases & Caching
Walk me through a safe RDS PostgreSQL/MySQL upgrade with a rollback plan (as you did at Intuit).
Databases & Caching · Basic level
Answer
For a major RDS upgrade, I avoid untested in-place changes on critical systems. I prefer blue/green deployment, logical replication, DMS, or a replica-style approach so most upgrade work and validation happens away from production before a controlled cutover.
Technical explanation
Major upgrades can change query plans, parameters, extensions, authentication behavior, reserved words, and client compatibility.
Blue/green reduces risk by creating a synchronized green environment where the new version can be tested before switchover.
Rollback must be designed before cutover; after writes hit the new version, rollback may require restore or reverse migration.
Hands-on example
Upgrade runbook:
1. Restore prod snapshot to staging and upgrade it.
2. Run app regression, migrations, batch jobs, and top SQL comparisons.
3. Create blue/green or logical target.
4. Freeze schema changes.
5. Cut over during approved window.
6. Monitor p95 latency, DB load, locks, error rate, and slow queries.
7. Keep old environment read-only until rollback window expires.
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