Tell me about a time you were responsible for a production database. What did you do to keep it healthy?

Note: Interviewers use this to find out whether you have actually carried an on-call pager or only worked on a laptop copy of a database. Give concrete routines, not adjectives.

Structure your answer around the three things every DBA is judged on:

• Backups you have actually restored. Say how often you took them (nightly logical dump plus binary logs for point-in-time recovery, for example) and — more importantly — the last time you rehearsed a restore. A backup nobody has restored is a guess.
• What you monitored. Replication lag, slow query log, connection count, buffer pool hit rate, disk headroom. Name the threshold that pages you.
• How you handled schema changes. Whether you used online DDL, pt-online-schema-change, or a maintenance window, and how you rolled back.

Close with an incident: what broke, how you noticed, how long recovery took, and the change you made afterwards so it could not happen twice.