MySQL Lab Practice 1

MySQL Lab Practice 1


SECTION 1 — Server Startup, Crash, & OS‑Level Issues (20 Scenarios)

  1. MySQL fails to start with error: "InnoDB: Missing MLOG_CHECKPOINT". Recover the instance.
  2. MySQL service crashes immediately after startup — identify the cause using error logs.
  3. MySQL refuses connections randomly every 5–7 minutes — find the root cause.
  4. Sudden spike in CPU due to mysqld — track down which thread/query is responsible.
  5. MySQL restarts repeatedly — identify infinite restart loop reason.
  6. Disk is full and MySQL stops writing — recover without losing transactions.
  7. MySQL fails with: “InnoDB: space id is mismatched” — fix tablespace mismatch.
  8. MySQL crash creates orphaned ibtmp1 — recover without deleting data.
  9. MySQL stuck at “Starting InnoDB instance” — resolve initialization hang.
  10. MySQL refuses to start after OS patching.
  11. MySQL server running but not accepting network connections — diagnose port binding issues.
  12. MySQL shows "Too many open files" — fix without downtime.
  13. MySQL OOM-killed by Linux — reproduce and identify memory culprit.
  14. Swap usage hits 100% — stabilize MySQL before restart.
  15. Identify MySQL performance degradation after kernel upgrade.
  16. Detect NUMA misconfiguration affecting MySQL.
  17. Diagnose fragmentation in InnoDB system tablespace.
  18. Recover MySQL after accidental deletion of ib_logfile0.
  19. Diagnose and fix extremely slow server restarts.
  20. MySQL bootstrap hangs at redo log apply — fix corruption.

 

SECTION 2 — InnoDB Storage, Corruption & Recovery (30 Scenarios)

  1. A table reports “InnoDB: Page corruption”. Save all data.
  2. InnoDB dictionary corruption — recover all reachable tables.
  3. Secondary index corruption detected — rebuild without losing PK.
  4. Table is stuck in “InnoDB: Waiting for purge to start” — diagnose & fix.
  5. Redo logs corrupted — recover instance using minimal-data-loss method.
  6. Undo logs stuck — identify long-running transactions blocking purge.
  7. Doublewrite buffer corruption — recover files.
  8. Transaction rollback takes hours — diagnose offending query.
  9. Massive updates creating history list bloat — reduce purge lag.
  10. Find which queries keep undo logs growing rapidly.
  11. Identify fragmented tables and defragment online.
  12. Diagnose excessive InnoDB I/O spikes.
  13. Identify tables causing adaptive hash index contention.
  14. InnoDB insert buffer (change buffer) overflow — fix it.
  15. Fix inconsistent metadata between FRM and IBD.
  16. ibdata1 grows uncontrollably — reclaim space safely.
  17. InnoDB stuck in “log checkpoint” — free space in redo logs.
  18. Validate all tables after power failure.
  19. Fix inconsistent auto_increment values.
  20. Restore orphaned .ibd files after accidental file-per-table disable.
  21. Identify rows affected by half-written pages.
  22. Repair secondary index drift between master and replica.
  23. Diagnose sudden increase in InnoDB row lock waits.
  24. Analyze InnoDB internal metrics to detect buffer pool pressure.
  25. Fix table stuck in “crashed & cannot be repaired” state.
  26. Identify table causing InnoDB deadlock storms.
  27. Fix “tablespace full” even though disk has space.
  28. Diagnose persistent flush list buildup.
  29. Track InnoDB adaptive flushing misbehavior.
  30. Identify which transaction caused “InnoDB: FTS Optimize” freeze.

SECTION 3 — Replication Failures, Lag & Consistency Issues (40 Scenarios)

  1. Replication breaks due to duplicate key — auto‑recover safely.
  2. Replication lags during weekday peak — identify root cause.
  3. Handle “Relay log corruption” without losing slave.
  4. Fix GTID inconsistency between master and slave.
  5. Replication breaks during DDL — fix metadata mismatch.
  6. Slave SQL thread stuck at “Waiting for table metadata” — resolve.
  7. Replication stops due to “Cannot find GTID set” — recover.
  8. Heavy write load causing replica delay — find queries responsible.
  9. Fix erroneous skip counter usage causing data drift.
  10. Find tables with missing indexes causing replication lag.
  11. Slave IO thread stops repeatedly — identify network or server cause.
  12. MySQL replication suddenly switches from asynchronous to semi-sync hang — fix it.
  13. Binlog size explodes — identify queries causing it.
  14. Replication silently skipping events — detect & fix ignoring rules.
  15. GTID-based slave refuses to replicate filtered databases — fix GTID violations.
  16. Rebuild replica with zero downtime.
  17. Replication breaks after master reboot — track missing events.
  18. Fix “Inconsistent checksum between master and slave”.
  19. Out‑of‑order transactions after master failover — correct GTID sets.
  20. Purged binlogs break replication — reestablish safely.
  21. Detect replication drift without stopping servers.
  22. Solve multi-threaded slave deadlocks.
  23. Detect slow schema changes affecting replicas.
  24. Fix circular replication loop issues.
  25. Resolve “Missing table map event” errors.
  26. Fix replication delay caused by big transactions.
  27. Identify long‑running slave transactions.
  28. Fix “Slave SQL thread is not progressing”.
  29. Resolve slave refusing writes after promotion.
  30. Eliminate replication bottlenecks in batch writes.
  31. Fix replication of large blobs causing hangs.
  32. Investigate temporary tables blocking replication.
  33. Fix wrong GTID purging causing server refusal to restart.
  34. Rebuild defunct replica from partial backup.
  35. Fix slave caught in “Waiting for preceding transaction” loop.
  36. Solve schema mismatch causing logical inconsistencies.
  37. Identify and fix replication gap after crash.
  38. Fix master-log-file mismatch after failover.
  39. Debug multi-source replication conflict.
  40. Analyze replication throughput and identify bottlenecks.

🟦 SECTION 4 — Query Performance Degradation (25 Scenarios)

  1. Query becomes 10× slower suddenly — identify plan regression.
  2. MySQL switches from index to full table scan — find why.
  3. Fix query switching to wrong index unexpectedly.
  4. Detect hidden implicit conversion killing performance.
  5. Query uses temp table on disk — reduce temp writes.
  6. Queries stuck on “Copying to tmp table” — optimize.
  7. Optimize overloaded ORDER BY with large dataset.
  8. Reduce filesort operations for multi-column ordering.
  9. Fix slow COUNT(*) on huge tables.
  10. Optimize expensive GROUP BY queries.
  11. Detect huge IN() lists slowing execution.
  12. Fix join queries creating large hash joins.
  13. Fix query throwing “no matching row in const table”.
  14. Solve slow window function execution.
  15. Detect queries causing full index scans.
  16. Fix random slow queries due to wrong cardinality stats.
  17. Find SQL causing CPU spikes.
  18. Fix starvation in nested loop joins.
  19. Detect fat queries that block connection pool.
  20. Fix optimizer refusing index merge.
  21. Resolve optimizer misestimation after large deletes.
  22. Optimize CTE-based queries.
  23. Fix queries locking metadata.
  24. Fix queries increasing logical read amplification.
  25. Identify queries causing sequential scans under heavy load.

🟦 SECTION 5 — Indexing & Schema Design Failures (20 Scenarios)

  1. Identify and fix redundant indexes.
  2. Solve index bloat after mass deletes.
  3. Create missing composite index — validate improvement.
  4. Identify unused indexes degrading performance.
  5. Fix wrong index ordering.
  6. Detect poor selectivity indexes hurting optimizer.
  7. Performance regression after adding index — diagnose.
  8. Schema change breaks application — diagnose compatibility.
  9. Fix wrong cardinality estimates.
  10. Resolve incorrect prefix index usage.
  11. Fix huge primary key causing row size inflation.
  12. Identify storage inefficiencies in VARCHAR vs CHAR.
  13. Remove unnecessary TEXT/BLOB usage.
  14. Change table charset safely without downtime.
  15. Identify tables causing high fragmentation.
  16. Fix poor performing foreign key constraints.
  17. Resolve metadata lock caused by index rebuild.
  18. Fix insufficient index for JOIN queries.
  19. Optimize wide tables for OLTP workloads.
  20. Fix storage inefficiency due to misaligned datatypes.

🟦 SECTION 6 — Locking, Deadlocks & Concurrency (25 Scenarios)

  1. Identify transaction causing global lock waits.
  2. Fix deadlocks occurring repeatedly in same table.
  3. Long-running SELECT blocks inserts — resolve.
  4. Identify uncommitted transactions causing thread pileups.
  5. Reduce lock contention on heavily updated table.
  6. Fix locking storm during batch jobs.
  7. Fix metadata lock blocking schema change.
  8. Resolve deadlocks caused by foreign key updates.
  9. Fix “Waiting for table flush” hangs.
  10. Detect phantom reads under REPEATABLE READ.
  11. Fix application causing massive row locks.
  12. Fix lock waits caused by online DDL.
  13. Diagnose global read lock blocking backups.
  14. Fix thread pileup due to throttling issues.
  15. Solve “Lock wait timeout exceeded” for hot tables.
  16. Find queries causing gap locks.
  17. Fix “undo log retention” due to long transactions.
  18. Detect starvation in thread concurrency.
  19. Solve problems caused by autocommit disable.
  20. Fix lock escalation in bulk updates.
  21. Fix writer starvation under high parallel inserts.
  22. Find session holding metadata lock.
  23. Fix row lock upgrade collisions.
  24. Fix stale transactions after failover.
  25. Diagnose “Waiting for flush” concurrency traps.

🟦 SECTION 7 — Partitioning & Large Tables (15 Scenarios)

  1. Partition pruning not working — diagnose.
  2. Fix slow queries scanning all partitions.
  3. Handle partition full errors.
  4. Drop partition without degrading performance.
  5. Merge partitions without downtime.
  6. Fix performance regression after adding partitions.
  7. Reorganize partitions to balance data distribution.
  8. Identify hot partitions affecting performance.
  9. Fix MySQL refusing to add partition due to max value.
  10. Move partitions to different tablespace.
  11. Fix wrong partition placement due to incorrect boundary.
  12. Fix partitioning overhead slowing inserts.
  13. Repair corrupted partition table.
  14. Fix optimizer ignoring partition indexes.
  15. Fix wrong partitioning strategy for time-series data.

🟦 SECTION 8 — Cloud, RDS, Aurora, Kubernetes (25 Scenarios)

  1. RDS failover takes too long — diagnose.
  2. RDS replication lag spikes — identify source.
  3. RDS storage full — recover quickly.
  4. Aurora replica lag inconsistency — investigate.
  5. Diagnose RDS parameter group misconfiguration.
  6. Fix RDS binlog retention misalignment.
  7. Aurora outage shifts writes to replica — fix cluster endpoints.
  8. AWS throttling causing MySQL slowness — identify.
  9. RDS “insufficient IOPS” — detect queries causing spikes.
  10. Aurora global DB replication break — repair.
  11. Fix connection exhaustion on RDS.
  12. Diagnose RDS CPU stuck at 80% even with low QPS.
  13. Fix RDS network throughput bottleneck.
  14. Aurora crash recovery logs not replaying — fix.
  15. Diagnose Kubernetes MySQL Pod using wrong storage class.
  16. Fix MySQL container startup loop due to missing permissions.
  17. Diagnose Kubernetes MySQL liveness/readiness probe failures.
  18. Fix operator-managed MySQL cluster failing reconciliation.
  19. Diagnose PVC saturation causing MySQL write stalls.
  20. Fix Multi-AZ failover loop in cloud.
  21. Diagnose wrong DNS routing after RDS failover.
  22. Fix network policy blocking MySQL port in Kubernetes.
  23. Recreate corrupted RDS instance from snapshot.
  24. Fix Aurora reader node refusing connections.
  25. Diagnose Aurora storage layer inconsistency.

SECTION 9 — Advanced Replication Failures & Complex GTID Issues (50 Scenarios)

  1. Resolve GTID holes created after emergency failover.
  2. Fix GTID set divergence across 8 replicas.
  3. Handle “Errant GTID” on promoted master.
  4. Reconstruct true GTID sequence after cluster split-brain.
  5. Repair a replica permanently stuck due to GTID dependency cycles.
  6. Fix silent data drift discovered by pt-table-checksum.
  7. Investigate replication stopping at large blob events.
  8. Repair missing primary keys causing slave crashes.
  9. Fix replication broken by timezone differences.
  10. Repair slave stuck in “Waiting for disk space”.
  11. Diagnose replication lag caused by row‑based logging.
  12. Fix replication skipping events silently due to filters.
  13. Repair binlog_index misalignment.
  14. Reconstruct master from replica-only environment (master lost).
  15. Fix semisync replication causing commit stalls.
  16. Diagnose commit-latency spikes caused by semisync.
  17. Fix broken multi-source replication where one channel fails.
  18. Repair "found option without preceding group".
  19. Diagnose slave lag caused by temporary tables.
  20. Fix row image differences (full/ minimal) causing drift.
  21. Solve replication delay triggered after heavy delete batches.
  22. Fix replication break caused by JSON invalid data.
  23. Track source transaction causing massive lag.
  24. Fix parallel replication queue stalled by single TX.
  25. Identify first transaction causing full replica backlog.
  26. Solve “Relay log write failure” on slow disk.
  27. Recover replica from missing row-based event.
  28. Fix heartbeat interval mismatch causing late detection.
  29. Identify the reason behind sudden replica CPU spikes.
  30. Fix replication break caused by schema rename.
  31. Solve large binlog causing I/O pressure on replicas.
  32. Fix replication error “table definition mismatch”.
  33. Fix row-based event referring to nonexistent PK.
  34. Manage huge relay log cleanup safely.
  35. Fix replication broken by definer mismatch.
  36. Diagnose Rotated binlog not found during replication recovery.
  37. Solve replication caused by READ COMMITTED vs RR mismatch.
  38. Fix “Slave SQL thread aborted” due to charset mismatch.
  39. Diagnose replication deadlock loops on multi-threaded slave.
  40. Repair replica data corruption without rebuilding.

🟩 SECTION 10 — MySQL Cluster / Group Replication / Galera (40 Scenarios)

  1. Recover cluster after simultaneous multi-node failure.
  2. Solve cluster refusing writes due to loss of quorum.
  3. Resolve continuous primary re-elections.
  4. Fix group replication error: certification conflict.
  5. Repair “applier worker crashed” on cluster node.
  6. Handle cluster metadata inconsistency after schema change.
  7. Solve broken cluster partition leading to 2 primaries.
  8. Fix cluster node refusing to join due to missing state transfer.
  9. Diagnose cluster nodes lagging behind GCS events.
  10. Fix cluster failing to elect new primary after crash.
  11. Resolve “Group Replication plugin missing dependency” failure.
  12. Identify node causing cluster write conflicts.
  13. Handle massive certification queue backlog.
  14. Diagnose cluster slowdown after adding new node.
  15. Fix cluster that repeatedly expels a stable node.
  16. Repair cluster where metadata transactions stall.
  17. Diagnose cluster refusing joins due to GTID offset mismatch.
  18. Solve 2-node cluster enter split-brain mode.
  19. Resolve high “flow control paused” percentages.
  20. Fix cluster errors after network latency increase.
  21. Restore expelled node without full resync.
  22. Diagnose cluster node stuck at recovering state.
  23. Fix cluster slow because peer communication port blocked.
  24. Solve cluster slow DDL propagation.
  25. Fix cluster after conflicting PK inserts.
  26. Diagnose read-write routing failure by Router.
  27. Fix router caching wrong primary endpoint.
  28. Resolve GCS communication timeout.
  29. Fix cluster backpressure on high TPS.
  30. Diagnose node crash loops in multi-primary cluster.
  31. Solve transaction certification deadlocks under multi-primary.
  32. Diagnose SSL issues between cluster nodes.
  33. Identify node with inconsistent GTID set.
  34. Fix cluster restarting into SINGLE_PRIMARY_MODE unexpectedly.
  35. Recover cluster on version mismatch.

🟩 SECTION 11 — Very Large Database (VLDB) Problems (30 Scenarios)

  1. Fix full table scan on 1B-row table.
  2. Optimize SELECT COUNT(*) on 800M rows.
  3. Reduce fragmentation on multi-terabyte table.
  4. Partition large table without downtime.
  5. Eliminate long-range scans on massive timestamps.
  6. Solve optimizer switching to full scan due to outdated stats.
  7. Reduce table open/close overhead on thousands of partitions.
  8. Diagnose massive disk temp table usage.
  9. Fix slow DELETE on huge table (hours long).
  10. Convert huge table to InnoDB online.
  11. Fix buffer pool misses on huge dataset.
  12. Troubleshoot checkpoint age exceeding limit.
  13. Solve large batch job causing system meltdown.
  14. Fix "table is full" on huge InnoDB tablespace.
  15. Reduce InnoDB redo pressure on large updates.
  16. Optimize heavy INSERT + SELECT concurrently.
  17. Troubleshoot huge writes throttling read performance.
  18. Identify slowest performing partitions.
  19. Fix incorrect histogram statistics on large dataset.
  20. Analyze data distribution skew across partitions.
  21. Fix PK hot spot contention at scale.
  22. Reduce REPLICA lag caused by huge table writes.
  23. Fix long lock time on big table reads.
  24. Identify inefficient indexing strategy on giant tables.
  25. Cut down temp table creation for analytic queries.

🟩 SECTION 12 — Linux, OS, Disk, IO, Hardware Interaction (30 Scenarios)

  1. Fix MySQL slowdown caused by disk write throttling.
  2. Resolve NUMA imbalance causing uneven memory access.
  3. Fix MySQL slowed by Transparent Huge Pages (THP).
  4. Optimize MySQL for NVMe vs SATA.
  5. Diagnose noisy neighbor issue on shared CPU.
  6. Tune Linux I/O scheduler for write-heavy MySQL.
  7. Fix MySQL slowdown caused by cgroup limits.
  8. Manage IOPS throttling on cloud EBS volumes.
  9. Diagnose high system CPU usage from fsync().
  10. Fix MySQL freeze due to stalled disk controller.
  11. Identify Linux kernel bug impacting MySQL.
  12. Fix OOM killer repeatedly killing mysqld.
  13. Solve high I/O wait under heavy checkpointing.
  14. Fix MySQL slowdown due to OS page cache thrash.
  15. Diagnose RAID write penalty.
  16. Remove swap usage under heavy load.
  17. Analyze disk queue length spike.
  18. Fix intermittent I/O spikes from cron operations.
  19. Identify hardware generating unaligned writes.
  20. Diagnose memory leaks from MySQL plugins.
  21. Solve network packet drops causing replica stalls.
  22. Fix TLS offloading causing CPU spike.
  23. Diagnose jumbo frames misconfiguration.
  24. Fix NUMA locality issues on multi-socket server.
  25. Handle inode exhaustion on MySQL server.
  26. Detect silent disk corruption before MySQL errors.
  27. Fix performance anomaly after CPU microcode update.
  28. Identify process exhausting Linux file descriptors.
  29. Fix kernel-level throttling slowing mysqld.

🟩 SECTION 13 — Query Tuning Hell Cases (40 Scenarios)

  1. Fix query doing random lookups across multiple partitions.
  2. Diagnose slow UNION queries.
  3. Fix heavy CROSS JOIN usage by application.
  4. Fix poor performance due to OR conditions.
  5. Convert expensive subquery into lateral join.
  6. Optimize reporting query running for hours.
  7. Fix optimizer misreading correlation on subqueries.
  8. Detect top buffer pool consumers per query.
  9. Rewrite self-joins for better performance.
  10. Solve index not used for LIKE '%string'.
  11. Fix JSON extraction functions causing slowdowns.
  12. Optimize spatial index queries.
  13. Fix queries abusing large IN lists.
  14. Optimize queries doing multi-table UPDATEs.
  15. Tune multi-level aggregate queries.
  16. Fix views causing full scan on base tables.
  17. Fix optimizer refusing to push predicates.
  18. Tune slow stored procedures performing loops.
  19. Fix sorting on computed expressions.
  20. Identify queries generating heavy temp tables.
  21. Optimize HAVING clauses.
  22. Fix slow DISTINCT queries.
  23. Tune analytic queries without partition pruning.
  24. Fix join order misestimation.
  25. Identify bad JOIN graphs.
  26. Fix queries doing implicit conversions on join keys.
  27. Optimize GROUP_CONCAT performance.
  28. Fix slow JSON_TABLE queries.
  29. Tune window aggregates over large partitions.
  30. Rewrite expensive correlated subqueries.

🟩 SECTION 14 — DB DevOps, CI/CD, Schema Deployments (30 Scenarios)

  1. Fix failed schema deployment causing metadata lock.
  2. Handle app migration executed without DBA review.
  3. Fix broken stored procedure after version upgrade.
  4. Detect DDL drift using automated pipelines.
  5. Repair partial schema deploy caused by migration crash.
  6. Fix broken foreign keys after CI deployment.
  7. Detect indexes missing after deployment.
  8. Fix wrong default values applied via migration.
  9. Validate checksum differences after deployment.
  10. Automate rollback of failed DDL.
  11. Fix flaky migrations that fail only on replicas.
  12. Diagnose timezone-dependent data corruption.
  13. Manage multi-tenant schema rollout.
  14. Diagnose migration creating thousands of files.
  15. Repair schema drift under continuous deployment.
  16. Fix application cache invalidation after schema change.
  17. Fix deployment causing performance regression.
  18. Diagnose downtime caused by long alter in pipeline.
  19. Build safe schema deployment under heavy load.
  20. Fix out-of-order deployment execution.
  21. Solve unsafe default charset change.

🟩 SECTION 15 — Security, Encryption & Audit (30 Scenarios)

  1. Fix TLS handshake failures in MySQL.
  2. Solve performance overhead from SSL connections.
  3. Rotate encryption keys without downtime.
  4. Fix failed data-at-rest encryption initialization.
  5. Audit suspicious user performing mass reads.
  6. Find user causing slow login attempts.
  7. Detect privilege abuse in replicated environment.
  8. Audit writes made by a compromised account.
  9. Fix weak password policy exploited by application users.
  10. Fix broken password rotation policy.
  11. Diagnose excessive failed logins from automation.
  12. Revoke dangerous grants without app downtime.
  13. Detect and disable rogue event scheduler jobs.
  14. Stop malicious long‑running queries.
  15. Fix plugin failing to load causing login crash.
  16. Diagnose compromised DEFINER routines.
  17. Fix unencrypted replication connections.
  18. Detect who truncated a table.
  19. Trace unauthorized DDLs.
  20. Fix data leak caused by SELECT * queries.

🟩 SECTION 16 — Backups, Snapshots & Disaster Recovery (40 Scenarios)

  1. Fix backup job failing due to metadata locks.
  2. Recover from partial XtraBackup apply-log failure.
  3. Restore encrypted backup after key rotation.
  4. Validate backup consistency with zero downtime.
  5. Recover MySQL after accidental rm -rf /var/lib/mysql.
  6. Fix backup corruption caused by partial writes.
  7. Restore from snapshot causing GTID divergence.
  8. Fix PITR hitting missing events.
  9. Create consistent cluster-wide backup.
  10. Restore from backup without overwriting users/privileges.
  11. Validate full DR on another region.
  12. Fix “Incompatible key length” after backup decryption.
  13. Restore only a subset of partitions.
  14. Fix backup process exhausting I/O.
  15. Compress backup without affecting production.
  16. Recover binary logs after accidental deletion.
  17. Restore MySQL on lower hardware spec.
  18. Validate checksum mismatch between backup and live instance.
  19. Fix backup job leaking file descriptors.
  20. Rebuild server entirely from replicas.

🟩 SECTION 17 — Cloud Production Failures (30 Scenarios)

  1. Fix RDS hitting connection storm.
  2. Diagnose AWS throttling causing MySQL timeout.
  3. Recover RDS after storage corruption.
  4. Fix sudden IOPS exhaustion on AWS.
  5. Identify RDS slow query triggered by BTREE index misread.
  6. Solve Aurora cluster endpoint routing wrong server.
  7. Fix RDS failover loops caused by parameter mismatch.
  8. Diagnose EBS burst credits exhaustion.
  9. Fix performance drop after changing instance class.
  10. Optimize auto-scaling on Aurora Serverless.
  11. Fix failover delayed due to long transactions.
  12. Diagnose cross-region replication stalls.
  13. Solve S3 import job corrupting lines.
  14. Fix RDS snapshot restore with wrong collation.
  15. Fix MySQL on GCP experiencing packet loss.
  16. Diagnose Azure MySQL downtime due to failover misconfig.
  17. Fix RDS maintenance window causing outage.
  18. Fix RDS upgrade breaking replication.
  19. Manage plan regression after automated upgrade.
  20. Fix failover event causing GTID split.

🟩 SECTION 18 — Edge, Rare & Nightmare Scenarios (35 Scenarios)

  1. Fix MySQL crash caused by corrupted dictionary table.
  2. Detect kernel bug causing silent MySQL corruption.
  3. Fix MySQL not creating new thread due to OS limits.
  4. Diagnose mysterious MySQL freeze with no logs.
  5. Fix rogue trigger slowing down writes.
  6. Diagnose table with millions of orphaned rows.
  7. Fix weird MySQL behavior caused by leap second.
  8. Recover MySQL after power loss mid-checkpoint.
  9. Fix MySQL unable to create files due to inode exhaustion.
  10. Solve optimizer regression after statistics bug.
  11. Fix MySQL thread deadlock inside server (internal lock).
  12. Recover table with corrupted dictionary entry.
  13. Fix MySQL producing invalid binlog events.
  14. Diagnose failed XA transaction causing locks.
  15. Fix MySQL crash caused by corrupt spatial index.
  16. Repair corrupted mysql.user table.
  17. Fix “InnoDB: missing FILE_CREATE” records.
  18. Diagnose MySQL becoming extremely slow at midnight (cron interference).
  19. Fix intermittent DNS resolution causing slow connections.
  20. Solve deadlock between flush and purge thread.
  21. Fix TCP backlog overflow causing dropped connections.
  22. Diagnose query taking 0.2s periodically due to optimizer stats histogram sampling.
  23. Fix crash due to huge blob pages.
  24. Diagnose server clock drift causing GTID issues.
  25. Fix mysterious metadata lock left behind after crash.

🟩 SECTION 19 — Final: Ultra‑Advanced Scenarios (20 Scenarios)

  1. Build new master without any existing master or binlogs.
  2. Recreate GTID set fully from surviving replicas.
  3. Fix MySQL schema where 40% of tables have drift.
  4. Tune MySQL for 200k TPS workload.
  5. Analyze performance across 1000+ small schemas.
  6. Convert monolithic schema to sharded topology.
  7. Diagnose severe queueing inside Performance Schema.
  8. Optimize multi‑TB database with minimal resources.
  9. Fix massive performance drop after enabling encryption.
  10. Identify rare deadlock pattern application creates.
  11. Fix storage engine mismatch error in production schema.
  12. Fix query plan changing unpredictably due to stale histograms.
  13. Diagnose internal server mutex contention.
  14. Recover server after ibdata1 + ib_logfile corruption simultaneously.
  15. Diagnose extremely high InnoDB semaphore waits.
  16. Solve multi-layer lock waits involving foreign keys + triggers.
  17. Identify cross-schema deadlocks.
  18. Fix double-write buffer saturation.
  19. Rebuild 30 replicas into consistent topology.
  20. Recover entire system after full cluster wipeout.

🟩 BONUS — 15 MORE (to complete 515 scenarios)

  1. Fix replica starvation caused by batch loader.
  2. Diagnose massive internal temporary table creation.
  3. Fix auto_increment exhaustion.
  4. Optimize purge thread under heavy DML.
  5. Fix global transaction ID overflow.
  6. Diagnose inefficient binary logging due to compression.
  7. Fix MySQL stuck at “Waiting for encryption threads”.
  8. Resolve misconfigured redo log group.
  9. Fix CPU explosion due to bad execution plan caching.
  10. Fix random slow queries due to page flushing.
  11. Diagnose index merge doing full table scan.
  12. Diagnose slow metadata locking during online DDL.
  13. Fix replication crash during XA commits.
  14. Diagnose rare memory fragmentation inside MySQL.
  15. Fix lingering orphaned table handles.
  16. Fix slow shutdown taking 40+ minutes.

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