Webhook Retry Storms: Exponential Backoff
Architectural guide to handling high-throughput SMS webhooks, preventing retry storms, and implementing idempotent queue workers.
Systematic Delivery Diagnostic Tree
Carrier Webhook Retry Loops
When an application server responds with HTTP 500, 502, 504, or times out (>15s), telecom carriers retry delivery up to 10 times with increasing frequency, overwhelming downstream systems.
Immediate HTTP 200 Acknowledgment Architecture
Webhooks should immediately return HTTP 200 with minimal validation and offload message parsing to background queues (Cloudflare Queues or Kafka).
Idempotent Deduplication Keys with Message SIDs
Because retried webhooks deliver identical payloads, worker consumers must record and check unique Message SIDs in Redis or D1 before processing.
Frequently Asked Questions
How do SMS providers handle webhook delivery timeouts?
Most providers retry delivery using exponential backoff over a 24-hour period. If your endpoint remains unresponsive, the provider will pause webhook dispatch.
How do you prevent duplicate message processing in webhooks?
Use the provider's unique MessageSid or MessageUUID as an idempotency key with an atomic database constraint or distributed lock.