Learning path
Reading Query Plans
Read EXPLAIN, find the slow query, and understand why the planner chose a plan.
backend, SRE · Intermediate · 3 courses · 7 simulations
The path
Courses, then incidents
Work through the courses, then practise the incidents — each step links to its page.
- Course Reading a Query Plan →
- Course How the Planner Chooses →
- Course Finding the Heavy Queries →
- query-performance Missing index on a hot endpoint →
- query-performance Wrong column order in a composite index →
- query-performance Stale statistics after a data-distribution change →
- query-performance Low-selectivity index trap →
- query-performance work_mem spill: the sort goes to disk →
- query-performance Slow pagination: deep OFFSET meltdown →
- query-performance N+1 query pattern (missing child-table index) →