6 min read
Zero-Downtime Postgres Migrations: The Three Patterns That Cover Most Cases
Zero-downtime migrations work when you split correctness from rollout: expand, backfill, dual-read or dual-write, validate, switch, then clean up.
Database Field Notes
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.
Featured Guides
Slow query optimization
Find the queries dragging your Postgres down, read their plans, and fix them in order of impact.
Read the guide →Index optimization
Which indexes to add, which to drop, and how to spot redundant index debt before it costs you writes.
Read the guide →Vacuum guide
How autovacuum works, when it falls behind, and how to keep bloat from eating your storage and your buffer cache.
Read the guide →Connection pooling
Sizing pools, PgBouncer modes, and how to stop idle-in-transaction sessions from exhausting max_connections.
Read the guide →Replication monitoring
Track lag, WAL throughput, and replication slots before they turn into stale reads or a full disk.
Read the guide →Browse by Topic
Backups and Durability
9 articlesBackups, restores, PITR, archive gaps, and recovery drills for PostgreSQL.
Cloud Providers
5 articlesAWS RDS, Azure Database for PostgreSQL, Google Cloud SQL, AlloyDB, and managed PostgreSQL monitoring notes.
Connections and Pooling
10 articlesConnection storms, pool saturation, PgBouncer behavior, and max_connections pressure.
CPU, Memory, and I/O
17 articlesCPU, memory, disk, temp files, checkpoints, buffers, and workload pressure.
Indexes
37 articlesIndex design, index debt, reindexing, constraint indexes, and evidence-driven DDL.
Locks and Transactions
22 articlesLock waits, deadlocks, blocking chains, idle transactions, and transaction hygiene.
MariaDB
56 articlesGalera clustering, InnoDB and Aria internals, replication, optimizer behavior, and MariaDB operations notes.
MySQL
107 articlesInnoDB internals, replication, locking, query performance, and MySQL operations notes.
pgvector and RAG
15 articlesHNSW, IVFFlat, recall, embedding search, and production RAG performance notes.
Replication and WAL
28 articlesReplica lag, WAL growth, failover readiness, hot standby behavior, and replication slots.
Slow Queries
38 articlesQuery plans, EXPLAIN ANALYZE, planner regressions, pagination, joins, and statistics.
SQL Server
47 articlesWait statistics, tempdb, Query Store, Always On availability groups, and SQL Server operations notes.
Vacuum and Bloat
16 articlesAutovacuum, dead tuples, bloat, wraparound, MVCC, freeze age, and visibility.
Latest Field Notes
7 min read
PostgreSQL VACUUM: Dead Tuples, Bloat, and Wraparound
VACUUM problems are cleanup debt. Dead tuples, bloat, frozen XIDs, and autovacuum lag turn normal queries into incident material when nobody is watching.
5 min read
Long-Running Transactions: The Quietest Way to Damage Your Postgres
Long transactions quietly hold back vacuum, keep locks alive, exhaust pools, and make old row versions stick around long after users moved on.
5 min read
Transaction Isolation in Postgres Without the Textbook Fog
Read Committed, Repeatable Read, Serializable. The textbook treatment puts most readers to sleep. Here is what each one actually means for your application.
5 min read
Deadlock Prevention in Postgres: Design It Out, Do Not Just Retry
Deadlocks are the symptom of a design that allows two transactions to hold each other's locks. The fix is rarely retry logic. Here is what to look for instead.
5 min read
ALTER TABLE Locks in Postgres: The Reference I Wish I Had Five Years Ago
ALTER TABLE is dangerous when you review syntax instead of locks. Some changes are instant, some queue behind writes, and some rewrite the whole table.
4 min read
VACUUM FREEZE in Postgres: The 4 a.m. Page You Can Prevent
Transaction ID wraparound is rare, dramatic, and entirely avoidable. Here is what FREEZE actually does, and the autovacuum settings that keep you out of single-user mode.
5 min read
Measuring Table Bloat in Postgres: The Question, Answered Honestly
Bloat measurement is useful only when it changes a cleanup decision. Learn when estimates are good enough, when pgstattuple is worth the cost, and what action follows.
6 min read
PostgreSQL Memory Tuning: shared_buffers, work_mem, and Cache
Postgres memory tuning is a budget problem. shared_buffers, OS cache, work_mem, maintenance work, and connection count all spend the same RAM.
5 min read
When the Postgres Disk Fills: A Playbook From the 2 a.m. End of It
Disk-full on a Postgres server is rarely just one thing. WAL, temp files, logs, and delayed cleanup arrive together. The recovery is mostly about what you prepared before.