Read EXPLAIN fluently, understand plan node types, pick the right indexes, and rewrite queries the planner struggles with.
A query that returns the right rows still needs to return them fast. These lessons cover reading EXPLAIN output, understanding what plan nodes mean, choosing indexes that match your queries, and rewriting patterns that trip up the planner.
Paired course
Query Optimization FundamentalsGo deeper with structured exercises, datasets, and production patterns.
EXPLAIN reveals the plan PostgreSQL chose without running the query. Reading cost, row estimates, and node type fluently is the starting point for all query analysis.
Indexes follow from your queries, not your tables. An index is a named trade: faster reads in exchange for slower writes. Only make trades you can justify.
Small SQL changes can have large performance effects. The most common slow queries share a recognizable EXPLAIN signature and a mechanical fix.
Go deeper
These lessons are the foundation. The book gives you the complete treatment, with real datasets you can run and the production patterns that turn thousands of lines of code into simple queries.
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