PostgreSQL performance tuning starts with a calm question: what changed? Workload, data volume, query plan, indexes, memory, locks, and vacuum behavior can all change the story.
This post is part of the DBApreneur starter series. The goal is to explain the topic in plain language, then give you practical checks or examples you can use in real work.
Start with the slow query
Do not tune the whole database first. Find the query, get the plan, check row estimates, and compare expected rows with actual rows. EXPLAIN ANALYZE is often where the truth begins.
Indexing basics
Indexes help reads, but they are not free. They add write overhead and storage. A good index matches a real query pattern: filters, joins, ordering, and selectivity.
Vacuum matters
PostgreSQL uses MVCC, so old row versions need cleanup. If vacuum falls behind, tables and indexes can bloat, statistics can drift, and performance can become unpredictable.
Useful checks
SELECT datname, numbackends, xact_commit, xact_rollback
FROM pg_stat_database;
SELECT relname, n_dead_tup, last_vacuum, last_autovacuum
FROM pg_stat_user_tables
ORDER BY n_dead_tup DESC;
Practical checklist
- Start with the problem you are trying to solve.
- Confirm the environment and version before applying any command.
- Test in a lab or lower environment first.
- Keep notes of what changed and why.
- Review performance, security, and rollback impact before production.
Final thought
Good engineering is rarely about memorizing commands. It is about understanding the shape of the system, asking better questions, and making changes that are boring in production. That is the kind of DBA work this series is trying to encourage.