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 report query ran in 26 seconds on PostgreSQL 11 and 480 milliseconds on MySQL 8 with identical SQL, then got slow again on PostgreSQL 12 for a new reason. The WITH clause means different things to each planner, and…
Our orders table got vacuumed three times a day and its relfrozenxid still crept 2 million xids a week — until one Tuesday the anti-wraparound vacuum read all 420 GB of it in a single afternoon. The freeze knobs, the…
We flipped password_encryption and pg_hba.conf in the same change window and locked out 41 of 46 roles on an inherited cluster. The correct order is the reverse — rotate passwords while pg_hba still says md5, then flip it last.
One Debezium-style connector on a busy primary cost us a third of a core, twenty percent more WAL, and — when the consumer stalled over a long weekend — 92 GB of retained WAL. The full cost sheet, and the…
Our orders table carried a 13.6 GB btree on a status column with five distinct values across 400 million rows — two years after upgrading to PostgreSQL 14. One REINDEX CONCURRENTLY brought it back at 2.4 GB. The upgrade grants…
During our hourly import burst, backends spent a third of their time in buffer write waits while the checkpointer dumped 25 GB in 90-second spikes. Smoothing the bgwriter flattened checkpoint IO and cut burst p99 from 400 ms to under…
Monday 09:00, the entire application tier was locked out: 'Host 10.0.4.17 is blocked because of many connection errors; unblock with mysqladmin flush-hosts'. A new Kubernetes liveness probe had spent the weekend opening TCP connections and closing them without a handshake.
The finance report had run with NOLOCK for two years to 'avoid blocking.' Then a reconciliation found the same invoice counted twice in one run and missing in the next — no dirty data involved, just an allocation-ordered scan walking…
A well-meaning engineer created forty-one indexes straight from dm_db_missing_index_details. Write latency doubled, three of the new indexes were never read once, and twelve were duplicates of each other with different column order. The DMV is a hint engine, not a…
Rotate MariaDB TLS files with FLUSH SSL, distribute trusted CAs first, and verify new client connections, account certificate requirements, and replicas.