ChatGPT, I’m trying to replace polling with webhooks in my product — what should I watch out for?

Replacing polling with webhooks is usually a good move, but there are a few important pitfalls to plan for. The big idea: polling is simple and wasteful; webhooks are efficient but operationally trickier.

What to watch out for

1. Delivery is usually at-least-once, not exactly-once

Webhook providers often retry on failures, which means your endpoint may receive the same event more than once.

What to do:

• Make your handler idempotent
• Store and dedupe by an event ID
• Treat repeated deliveries as normal

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2. Webhooks can arrive out of order

If multiple events are emitted quickly, network timing can cause them to arrive in a different order than they were created.

What to do:

• Don’t assume order
• Use timestamps/version numbers where possible
• Fetch the latest state from the source if ordering matters

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3. Your endpoint must be highly reliable

If your server is down, slow, or returns errors, events may be retried later—or dropped if the sender gives up.

What to do:

• Return a 2xx quickly
• Process asynchronously if work is heavy
• Use queueing/background jobs
• Monitor error rates and latency

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4. Signature verification and security matter a lot

Unlike polling, where you initiate the request, webhooks send data to you. You need to confirm the request is really from the expected sender.

What to do:

• Verify HMAC/signatures or shared secrets
• Use HTTPS only
• Consider IP allowlisting only as a secondary measure
• Reject unsigned or malformed requests

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5. Retries can create duplicate side effects

If your handler does work before acknowledging the request, a timeout can cause the sender to retry and repeat the work.

What to do:

• Make processing atomic where possible
• Write the incoming event to durable storage first
• Acknowledge quickly, then process later
• Design downstream actions to be idempotent too

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6. You need a plan for backfill and missed events

Polling naturally re-checks state; webhooks can miss events if your system was offline too long or the provider’s retry window expires.

What to do:

• Keep a fallback sync/polling mechanism
• Support “replay” or “list events since cursor” if available
• Periodically reconcile against source-of-truth data

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7. Event schemas can change

Webhook payloads may evolve over time, and brittle parsing can break your integration.

What to do:

• Version your webhook contract if you control it
• Be tolerant of extra fields
• Validate required fields carefully
• Have tests for old/new payload variants

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8. Rate limits and burstiness

Webhooks can arrive in bursts, especially after retries or when many events occur at once.

What to do:

• Use a queue or buffer
• Apply backpressure safely
• Ensure your processing workers can scale
• Watch your own downstream APIs and DB limits

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9. Observability becomes essential

With polling, you can often diagnose issues by looking at the polling loop. With webhooks, failures can be more invisible.

What to do:

• Log event IDs, timestamps, signatures status, and processing outcomes
• Track retries, duplicates, failures, and lag
• Build dashboards and alerts

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10. Some actions still need polling or reconciliation

Not everything should switch to webhooks. Webhooks are great for “something changed” notifications, but not always enough for full consistency.

Good hybrid pattern:

• Webhooks for near-real-time updates
• Periodic polling/reconciliation for safety

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A good webhook implementation usually looks like this

1. Receive request
2. Verify signature/authenticity
3. Store event durably
4. Return 2xx immediately
5. Process event asynchronously
6. Deduplicate and handle idempotently
7. Reconcile periodically with the source system

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Questions to ask before switching

• Can I tolerate duplicate and out-of-order events?
• What happens if my endpoint is down for 10 minutes? 1 hour?
• Do I have a unique event ID for deduplication?
• How will I verify authenticity?
• Do I have a fallback reconciliation strategy?
• Can my system absorb bursts?

If you want, I can also give you:

1. a webhook implementation checklist, or
2. a reference architecture for moving from polling to webhooks safely.