Hard Database Administrator questions

32 questions · 20 points each for a correct first answer.

1. 1.Fixing a recurring deadlocklocking, transactionshard
2. 2.Transaction ID wraparoundpostgresql, mvcchard
3. 3.Partition pruningpartitioning, query-tuninghard
4. 4.Choosing a shard keysharding, architecturehard
5. 5.Index ignored because of a functionindexing, postgresqlhard
6. 6.InnoDB gap locksmysql, lockinghard
7. 7.Avoiding split-brainhigh-availability, replicationhard
8. 8.Disk filling with WALreplication, postgresqlhard
9. 9.Two doctors go off calltransactions, isolation-levelshard
10. 10.Commits hang with sync replicationreplication, high-availabilityhard
11. 11.Prepared statement slows down laterquery-tuning, postgresqlhard
12. 12.Estimates wrong for city and zip codequery-tuning, postgresqlhard
13. 13.Index-only scan still reads the tableindexing, mvcchard
14. 14.Logical replication stopped after a migrationreplication, postgresqlhard
15. 15.pg_upgrade --link and rollbackpostgresql, upgradeshard
16. 16.pg_wal growing without limitbackup-recovery, postgresqlhard
17. 17.Errant GTIDs block failovermysql, replicationhard
18. 18.Online schema change tools for MySQLmysql, schema-changeshard
19. 19.Unique email on a partitioned tablepartitioning, postgresqlhard
20. 20.Deleting old data every monthpartitioning, postgresqlhard
21. 21.Primary demoted when etcd is unreachablehigh-availability, postgresqlhard
22. 22.WAL volume spikes after checkpointspostgresql, performancehard
23. 23.What encryption at rest protectsdatabase-securityhard
24. 24.Row-level security not applieddatabase-security, postgresqlhard
25. 25.Risky SECURITY DEFINER functiondatabase-security, postgresqlhard
26. 26.Indexes bloat on a counter tablepostgresql, performancehard
27. 27.Random UUID keys slow down insertsindexing, data-modellinghard
28. 28.Rejoining the old primaryhigh-availability, replicationhard
29. 29.OOM killer after raising work_mempostgresql, performancehard
30. 30.Restore takes longer than the RTObackup-recovery, high-availabilityhard
31. 31.Locks held by nobodytransactions, postgresqlhard
32. 32.Faster commits with a durability costmysql, transactionshard