Unbounded fan-out / no concurrency cap
Part of the Cost controls check · fix arrives as a guide
What it is
A set of async operations is dispatched all at once — commonly Promise.all over an array whose length is data-dependent — with no cap on how many run concurrently.
Why it matters
It works on ten items and takes down a dependency on ten thousand. The fan-out exhausts connection pools, trips downstream rate limits, and can exceed the function's memory before any of it completes.
How to fix it
Run the batch through a concurrency limiter with a fixed ceiling, or chunk it and await each chunk. Pick the limit from what the slowest downstream dependency can absorb, not from what the runtime allows.
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