Webhooks vs Polling

Being notified when something changes vs repeatedly asking.

Backend Engineer · Mid-level Frontend Engineer · Mid-level Data Engineer · Mid-level

Also known as: webhooks vs polling, push vs pull http, polling vs webhooks

When your system needs to know about another system’s events, there are two shapes. Polling asks repeatedly (“anything new? anything new?”); webhooks get told (the source POSTs to your URL when something happens). Push versus pull over HTTP.

polling:  you ──GET /events──▶ source, every 30s (mostly "nothing new")
webhooks: source ──POST /your-hook──▶ you, only when something happens

Webhooks win on latency and efficiency — near-instant delivery, no empty requests — at the cost of operating a public endpoint (verify signatures, handle retries, stay idempotent). Polling wins on simplicity and control — no inbound surface, you set the pace — at the cost of delay and wasted requests.

The classic mistakes:

Polling a huge interval for urgent events. Thirty-minute polls for fraud alerts guarantee staleness. Match frequency to the event’s urgency, or switch to push.
Hammering with short polls. One-second polling from thousands of clients is a self-inflicted DDoS. Respect rate limits, back off, use conditional requests and cursors.
Unauthenticated webhook endpoints. A public URL that acts on any POST is an invitation. Verify signatures and timestamps on every delivery.
Assuming webhook delivery. Webhooks retry and can still be missed; critical flows need reconciliation (periodic poll or provider status checks) alongside push.
Non-idempotent webhook handlers. Retries deliver duplicates; handlers must dedupe by event ID.
No cursor on polls. Re-fetching “everything recent” without a since-token duplicates and skips. Paginate by cursor or timestamp.
Choosing once and forever. Start with polling for simplicity, graduate to webhooks where latency or volume demands it. Many systems run both: webhooks live, polls reconcile.

The pairing: webhooks for now, polling for certainty. Push delivers fast; pull verifies. Together they cover what either alone guarantees poorly.