Rate limits, backoff, idempotency and retries

Rate limits, backoff, idempotency and retriesthe four words that make plumbing production-grade

Third-party APIs throttle you, fail intermittently and occasionally double-process. Production code expects all three. Idempotency is the one candidates miss most and it is the one that prevents charging a lead twice or creating duplicate CRM records.

POST /v1/contacts
Idempotency-Key: lead-7f3a9c-2026-06-15   # same key => server dedupes the create

# client retry loop (pseudocode)
for attempt in 1..5:
    res = send(request)
    if res.status == 429 or res.status >= 500:
        wait(min(2 ** attempt, 30) + jitter)   # exponential backoff + jitter
        continue
    break   # success or a 4xx we should not retry

• Rate limit - respect the provider’s ceiling; on a 429, back off rather than hammering.
• Backoff - wait longer after each failure (exponential), with jitter so many clients don’t retry in lockstep.
• Idempotency key - a stable key per logical operation so a retry re-runs safely instead of duplicating.
• Retry only the retryable - retry 429s and 5xx; do not retry a 400, which means your request is wrong.