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 single-threaded applier turns a busy source's parallel writes into a serial queue, and Seconds_Behind_Master will smile at you while it grows. How the parallel applier really decides what can run concurrently, and how to measure lag honestly.
Seconds_Behind_Source is the most quoted and least trusted replication metric in MySQL. This deep dive covers heartbeat-based lag measurement, multi-threaded replica tuning, and the big-transaction lag pattern.
Replication filters diverge replicas without raising a single error, and source-side filters quietly gut your point-in-time recovery. Here is how each layer actually fails.
A replica that cannot survive kill -9 is a replica you rebuild at 3 a.m. This covers relay_log_recovery, the repository history that made replicas crash-safe, GTID auto-positioning, and why you should crash replicas on purpose.
A crashed replica can come back looking perfectly healthy while quietly diverging. Here is the position-tracking machinery, the replay and skip failure modes, and the config that makes crashes boring.
innodb_redo_log_capacity replaced the old log file settings in 8.0.30. Checkpoint age, the async and sync flush thresholds, and the counters that warn you before a write burst stalls the server.
InnoDB skips transaction bookkeeping for known read-only transactions — but an open read view still pins purge. The autocommit=0 ORM trap, replica read-only flags, and how to measure the win.
Prepared statements are per-connection state with a server-wide cap. Prepared_stmt_count, error 1461, the ORM leak pattern, and why per-query prepare is the worst of both protocols.
MySQL partitioning works until it collides with foreign keys; PostgreSQL's declarative partitioning composes with the rest of the schema. A practitioner's comparison of pruning, partition-wise operations, and maintenance.
Partitioning solves data-lifecycle problems, not performance problems. Field notes on verifying pruning, automating partition maintenance, living with the foreign-key restriction, and knowing when to say no.