Idempotency keys vs dedup filters: stopping doubles two very different ways.

Idempotency keys vs dedup filters: stopping doubles two very different ways.

HEARD: every automation builder eventually ships a duplicate order or a double email, then bolts on a 'has this run before?' filter. That dedup check races. Two triggers fire at once, both pass the check, both run.

The real fix, per the engineers who've been burned:
— Idempotency key on the action itself: the downstream API rejects the second call. Bulletproof.
— Dedup filter in the flow: fine for low concurrency, leaky under load.

If your tool supports passing an idempotency key, use it. Filters are a hope, not a guarantee. Watch this.