Source code
Performance
Cost
N+1 DB queries — per-ID fetch inside map()
Part of the Scalability antipatterns check · fix arrives as a guide
What it is
A database query runs inside a loop or a map over a collection, issuing one round trip per item instead of one for the set.
Why it matters
The cost scales with the row count, so it is invisible with seed data and a timeout with real data. A hundred-item list becomes a hundred sequential round trips, each paying full network latency.
How to fix it
Collect the ids first and fetch them in a single query with an IN clause, or express the relationship as a join. Where the shape makes that awkward, batch the lookups through a loader that coalesces them per tick.
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