Notes for the problems that show up after launch: bad plans, awkward migrations, index debt, vacuum pressure, replica lag, and the small decisions that keep PostgreSQL, MySQL, MariaDB, and SQL Server easier to operate.
Find the queries dragging your Postgres down, read their plans, and fix them in order of impact.
Read the guide →Which indexes to add, which to drop, and how to spot redundant index debt before it costs you writes.
Read the guide →How autovacuum works, when it falls behind, and how to keep bloat from eating your storage and your buffer cache.
Read the guide →Sizing pools, PgBouncer modes, and how to stop idle-in-transaction sessions from exhausting max_connections.
Read the guide →Track lag, WAL throughput, and replication slots before they turn into stale reads or a full disk.
Read the guide →
Backups, restores, PITR, archive gaps, and recovery drills for PostgreSQL.
AWS RDS, Azure Database for PostgreSQL, Google Cloud SQL, AlloyDB, and managed PostgreSQL monitoring notes.
Connection storms, pool saturation, PgBouncer behavior, and max_connections pressure.
CPU, memory, disk, temp files, checkpoints, buffers, and workload pressure.
Index design, index debt, reindexing, constraint indexes, and evidence-driven DDL.
Lock waits, deadlocks, blocking chains, idle transactions, and transaction hygiene.
Galera clustering, InnoDB and Aria internals, replication, optimizer behavior, and MariaDB operations notes.
InnoDB internals, replication, locking, query performance, and MySQL operations notes.
HNSW, IVFFlat, recall, embedding search, and production RAG performance notes.
Replica lag, WAL growth, failover readiness, hot standby behavior, and replication slots.
Query plans, EXPLAIN ANALYZE, planner regressions, pagination, joins, and statistics.
Wait statistics, tempdb, Query Store, Always On availability groups, and SQL Server operations notes.
Autovacuum, dead tuples, bloat, wraparound, MVCC, freeze age, and visibility.
The sync job double-counted rows for three weeks because someone said 'change tracking' and someone else heard 'CDC'. What each feature actually captures, what each one costs, and a four-question test for picking the right one.
The app said the database was down; the database said CPU was twelve percent and forty-three sessions were queued behind one sleeping connection holding a lock. How I walk a blocking chain to its head and decide whether to kill…
The backups had been succeeding for eight months; the restores had never been tried. FULL/DIFF/LOG chain design as an RPO/RTO contract, what silently breaks the log chain, and why only a restore drill proves anything.
The dashboard said SYNCHRONIZED while the readable secondary served twenty-minute-old data. Send queue and redo queue are different numbers; here is what each one means, what synchronous commit really guarantees, and how to measure RPO.
Codebases that grew up on MySQL 5.x are full of workarounds for missing CTEs and window functions. Here is what those queries were compensating for, and their modern rewrites.
A single PostgreSQL query can consume work_mem many times over. Understanding the per-node multiplier is the difference between fast sorts and an OOM-killed primary.
full_page_writes protects you from torn pages but can dominate WAL volume. How checkpoints set the FPI rate, what wal_compression with lz4 or zstd buys you, and how to measure WAL with pg_stat_wal.
Expired object-store credentials made archive_command exit 1 at 02:11; by 07:40 pg_wal held 380 GB on a 500 GB volume. The failure was visible for hours in pg_stat_archiver — the view almost nobody graphs.
One word took our nightly staging load from 40 minutes to 9: UNLOGGED. Two months later a failover emptied the table and nobody on call could explain why. The semantics are absolute — if someone tells you.
Dead tuples climbed for days, autovacuum ran constantly, and pg_stat_activity showed nothing. The culprit was one row in pg_prepared_xacts, eleven days old, left by a Java service that crashed mid-commit.