Practical mini-book
Indexes Without Magic
How to read query plans and make the database do less work
Constantin Potapov
Senior Python Backend / R&D Engineer
PostgreSQL · MySQL · ORM
For backend developers who have at least once said the dangerous phrase «we just need to add an index here». Not spells but mechanics: why one index saves your evening, another changes nothing, and a third quietly chokes writes.
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What's inside
Five parts — from an honest talk about what an index is for to diagnostics, anti-patterns and a final cheat sheet.
Reality first
What an index is really for, how the database finds rows, and why «just add an index» is more often self-soothing than a plan.
Core constructs
B-tree, composite indexes and column order, selectivity, covering and partial indexes, uniqueness as a business rule.
Beyond B-tree
Text, JSON and geography: GIN, trigrams, functional and spatial indexes — the index type that matches the question.
Diagnostics
How to read EXPLAIN without guessing, and a practical algorithm for designing indexes from load, not from the schema.
Mistakes and a cheat sheet
When an index becomes ballast, why the ORM doesn't repeal database physics, anti-patterns and a final cheat sheet.
In short, the whole book is about one rule:
«A good index isn't the one that exists. A good index is the one after which the database does less work — and you can prove it.»
About the author
Constantin Potapov — Senior Python Backend / R&D Engineer. Works with Python, Django, FastAPI, PostgreSQL, MariaDB, Redis, Docker, Linux, integrations and engineering tooling.
The main professional habit is not to trust a beautiful explanation until it has passed through code, data and a reality check. A database isn't impressed by a developer's confidence and doesn't speed up from the team's good mood.
Take the book and stop guessing from the slow query log
A short engineering book about discipline: first understand the query, then change the schema. Less magic, more observable work.
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