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mediumSystem Design

How do you read EXPLAIN ANALYZE — cost, actual time, rows, and Buffers?

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01

Understand the problem

Decode execution plans, spot cardinality misestimates, and use BUFFERS/SETTINGS to debug I/O.

explainquery-planpostgres
02

Attempt it yourself

Sketch your approach before reading the solution — that's what interviews test.

Nudge consolestandby

Stuck? Beam a request up — the console returns a conceptual nudge that guides your logic without spoiling the implementation.

03

Study the solution

EXPLAIN shows estimates; EXPLAIN (ANALYZE, BUFFERS) actually runs and shows actual time, rows, loops, and Buffers: shared hit/read. A 10× gap between estimated and actual rows means stale stats — run ANALYZE.

Solution ready — 2 min read

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04

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Transmission complete // awaiting log

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STREAK ALIVE.

Dossier 40 of 70 decoded in the SQL track. One more won't hurt.

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