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---
title: PostgreSQL Indexing Basics for Faster Queries
description: Learn PostgreSQL indexing fundamentals, when to add B-tree indexes, and how to avoid over-indexing that slows down writes.
date: 2026-03-07
tags: postgresql, database, indexing, sql
---

Indexes can dramatically improve PostgreSQL read performance, but they are not free.

## What an index does

An index is a data structure that helps PostgreSQL locate rows faster without scanning an entire table.

For most equality and range lookups, B-tree is the default index type.

## When to add an index

Consider indexing columns used in:

- `WHERE` filters
- `JOIN` conditions
- `ORDER BY` clauses

Start from real slow-query data, not assumptions.

## Avoid over-indexing

Each index adds storage overhead and slows down inserts/updates/deletes. Too many indexes can hurt overall throughput.

## Verify with EXPLAIN

Use `EXPLAIN (ANALYZE, BUFFERS)` to compare query plans before and after indexing.

Key signs of improvement:

- Lower execution time
- Fewer shared buffer reads
- Better row estimate accuracy

Indexing is most effective when paired with query tuning and realistic workload testing.