Lesson 05 · 12 min
N+1 and DataLoader
Ten books, ten queries for authors. DataLoader makes one.
12 minLesson 5 of 9Practice includedAsk AI on any point
The Book.author resolver runs for each book separately. A list of 50 books is 1 query for books and 50 for authors. DataLoader collects every load(id) within one event loop tick and makes one batch query WHERE id IN (…), and it caches results within the request.
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