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PostgreSQL performance: EXPLAIN, indexes and when to switch databases

Find the slow query with EXPLAIN and fix it with the right index

Data reviewed on Oct 29, 2026 · LLM Stats indexes and official prices

The data, today

The context

When an application gets slow, the database is usually the culprit, and the most frequent cause is a query reading far more rows than needed. Before upgrading a plan or changing engines, measure: EXPLAIN ANALYZE shows how PostgreSQL runs the query, how many rows it expected and how many it actually read.

The right index often turns seconds into milliseconds, but it has a cost too: it takes space and slows writes. That is why you should create the ones your real workload needs, not one per column. If after optimizing you still need more capacity, the database catalog lets you compare price, limits and billing model.

What to decide

  1. 1

    How do I find the slow query?

    Turn on slow-query logging or the engine's statistics, sort by total time and start with the ones that accumulate the most. A 50 ms query run a million times weighs more than a 5 s query run once.

  2. 2

    How do I read an EXPLAIN plan?

    Look for sequential scans on large tables, row estimates far from the real counts and sorts spilling to disk. Codifly's index guide shows before-and-after examples with the exact changes.

  3. 3

    When do I switch databases?

    When you have already optimized and the limit is capacity, connections or cost, not before. Compare each provider's billing model and limits in the catalog against your load, and remember that migrating has its own cost.

Common mistakes

  • Creating an index on every column without measuring write cost.
  • Upgrading the plan before looking at the most expensive queries.
  • Measuring with test data far smaller than production.

Tools and comparators

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No provider pays for its position. Indexes come from LLM Stats; prices from each provider's standard API. How we measure

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