Webhooks vs Polling for Data Sync
Two opposite ways to learn 'something changed'
Polling means your system periodically asks a source ('has anything changed since I last checked?') on a fixed schedule — every 5 minutes, every hour, every night. Webhooks mean the source pushes a notification to your system the instant something happens, and your system reacts to that push rather than asking. Both ultimately move the same data; the difference is who initiates the exchange and how quickly changes propagate.
Webhooks vs polling for marketing data sync
| Dimension | Webhooks | Polling |
|---|---|---|
| Latency | Near-instant (seconds) | Bounded by poll interval (minutes to hours) |
| Load on source system | Low — source only sends on actual change | Higher — repeated requests even when nothing changed |
| Reliability guarantees | Source may retry, but delivery isn't always guaranteed; can be missed if your endpoint is down | Self-healing — next poll catches whatever was missed |
| Implementation complexity | Requires a publicly reachable, authenticated receiving endpoint | Simpler — just a scheduled job calling a documented API |
| Best fit | Time-sensitive triggers (cart abandonment, form submission, payment events) | Bulk reporting data, anything tolerant of some staleness |
Webhook delivery is not guaranteed exactly-once
Source platforms (Stripe, Shopify, HubSpot) typically retry webhook delivery on failure, which means your receiving endpoint must tolerate — and correctly handle — the same webhook arriving more than once. Treating webhook delivery as 'fires exactly once, in order' is one of the most common integration bugs in marketing engineering; webhook payloads routinely arrive duplicated, occasionally out of order, and in rare outage scenarios, not at all.
export async function handleShopifyWebhook(req: Request) {
const payload = await req.json();
const eventId = req.headers.get("x-shopify-webhook-id");
// Idempotency check: have we already processed this exact event?
const alreadyProcessed = await db.webhookEvents.findUnique({
where: { eventId },
});
if (alreadyProcessed) {
return new Response("ok", { status: 200 }); // ack without reprocessing
}
await db.webhookEvents.create({ data: { eventId, receivedAt: new Date() } });
await processOrderUpdate(payload);
return new Response("ok", { status: 200 });
}A webhook-only integration has no recovery path if your endpoint goes down
The hybrid pattern most mature integrations converge on
Use webhooks for latency-sensitive triggers where speed matters (real-time personalization, immediate lead routing), but never treat them as your only source of truth. Run a lower-frequency reconciliation poll against the same source as a safety net, and design your data model so re-processing an event you already have (whether from a duplicate webhook or a reconciliation poll re-fetching it) is a safe no-op rather than a double-count — which is exactly the idempotency discipline needed regardless of which transport delivered the event.
What's Next?
Handling duplicate or out-of-order delivery safely is really an instance of a more general integration principle — designing every operation so that running it more than once produces the same result as running it once.
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