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.
A table with one million live rows was holding five million dead ones, and queries were scanning all six. Understanding xmin, xmax, and how PostgreSQL decides what a query can see explains where the dead rows come from.
Everyone learns about transaction ID wraparound eventually. Then one day the log says 'MultiXactId members limit exceeded' and you discover PostgreSQL has a second counter that can run out — and it's usually your foreign keys filling it.
Every query takes lightweight relation locks you never think about. Cross the fast-path limit of 16 per backend, usually via heavy partitioning, and the shared lock manager turns into a bottleneck under concurrency.
LISTEN/NOTIFY is a lovely way to push events without extra infrastructure, until the global notify queue fills, a slow listener blocks commits, and you learn it was never built to be your message bus.
A single connection sitting in 'idle in transaction' can hold locks, pin the vacuum horizon, and quietly bloat every table in the database. I learned this the hard way from a debugger someone left paused overnight.
Long analytics queries on our replica kept getting cancelled mid-run. Turning on hot_standby_feedback stopped the cancellations instantly — and then the primary started bloating. That trade is the whole story.
Foreign tables look local, which is the problem. A join the planner can't push down pulls an entire remote table across the network row by row, and a clean-looking query becomes a multi-minute transfer.
The planner assumes your columns are independent. When they're actually correlated, its row estimates collapse, it picks a nested loop over a hash join, and a fast query becomes a slow one. CREATE STATISTICS fixes the math.
Swapping two rows' unique values failed halfway through with a duplicate-key error, even though the end state was perfectly valid. Deferrable constraints let PostgreSQL check at commit instead of after every row.
A nightly export OOM-killed itself trying to load ten million rows into memory at once. The fix wasn't more RAM — it was telling PostgreSQL to hand the rows over a batch at a time with a server-side cursor.