Operations
Idempotency
Idempotency is the property that running an operation multiple times produces the same result as running it once. Critical for webhooks (which often fire multiple times) and any automation that affects state. Implementation: idempotency keys (UUIDs) recognised by downstream APIs.
More detail
Stripe webhooks fire 1-3 times per event. Without idempotency, you'd send 3 welcome emails, create 3 CRM records, and credit 3 GL entries. With idempotency, you check 'have I seen this event_id before?' before acting. Tools like Stripe, GitHub, and Slack respect idempotency keys you supply. Aiprosol's Workflow Automation Playbook documents idempotency as one of 7 core production patterns.