Cookbook recipe

Eliminate N+1 queries with LATERAL joins

Applies to PostgreSQL 13–17 Last reviewed May 2026 Grounded in source

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A production experience capsule based on real incident patterns.

Why It Matters

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Estimated investigation4 min

Scenario

Your app runs one query per parent row to fetch its latest child. A LATERAL join does it in a single round trip. Diagnose it Fetch the top child per parent in one query: SELECT u.id,…

Investigation Path

Your app runs one query per parent row to fetch its latest child. A LATERAL join does it in a single round trip.

Diagnose it

Fetch the top child per parent in one query:

SELECT u.id, last_order.*
FROM users u
CROSS JOIN LATERAL (
  SELECT * FROM orders o
  WHERE o.user_id = u.id
  ORDER BY o.created_at DESC
  LIMIT 1
) AS last_order;

Why it happens

N+1 patterns send a query per row from the application, adding network and planning overhead per call. LATERAL lets a subquery reference the outer row so the database does the per-row lookup set-based.

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Related & next steps

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