AZ400-Q: combine canary with schema evolution
A canary release uses a new application version that writes an additional field. Older instances remain active during rollout. What schema strategy reduces compatibility risk?
- A) Drop old columns before starting the canary.
- B) Add backward-compatible changes first, run mixed versions safely, then remove obsolete structures only after old versions are gone. ✓
- C) Require all clients to update simultaneously.
- D) Disable database backups.
Answer: B. Expand-then-contract patterns allow old and new application versions to coexist during progressive release.
Why not the others: Destructive/simultaneous/no-backup choices remove rollback and compatibility safety.
Related
canary-deployment · deployment-automation · rollback-strategy