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 NVMe array could stream 3 GB/s and the range query crept along at 60 MB/s. One GUC explained the gap: effective_io_concurrency was 1, so the kernel heard about pages one at a time.
The planner is only as good as its statistics. When autoanalyze lags behind a bulk load, the bad plans arrive long before the next analyze run does.
Most MySQL SQL runs on PostgreSQL unchanged. This post catalogs the part that does not: quoting, upserts, LIMIT, GROUP BY strictness, string functions, and the silent integer division trap.
pgloader is the fastest way to move a MySQL schema and its data into PostgreSQL, but it is not a full migration. These field notes cover the casting rules, the gaps, and the verification pass.
performance_schema has a reputation for overhead it no longer deserves. Field notes on which instruments and consumers to enable, how to measure the memory cost, and how digests catch query regressions before customers do.
Your ORM will connect to PostgreSQL on day one and still surprise you for weeks. These are the behavior changes I watch for: case sensitivity, booleans, upserts, RETURNING, and transaction aborts.
CTEs and window functions made MySQL 8.0 queries readable, and occasionally much slower. Field notes on derived_merge, materialization, window frame costs, and the cases where the old JOIN still wins.
VARCHAR(255) is a MySQL-era reflex with real historical reasons behind it. Here is where the habit came from, why PostgreSQL teams reach for text plus CHECK constraints, and which performance claims survive scrutiny.
Collations decide what counts as equal, which indexes work on JOINs, and which queries throw mixed-collation errors. Field notes on choosing between utf8mb4_0900_ai_ci, general_ci, and bin, and migrating safely.
Undo growth means a snapshot is pinning purge. How innodb_undo_log_truncate reclaims space, managing tablespaces with CREATE and DROP UNDO TABLESPACE, and the stuck-report incident shape.