Webhooks vs API Polling: When to Use Each (and Why It Matters)

Both webhooks and polling let your application react to changes in external systems. But they have opposite architectures, different failure modes, and different costs. Choosing the wrong one is a common source of unnecessary latency, wasted API quota, and architectural debt.

How They Work

Polling: Your application calls an API on a schedule to check whether anything changed.

t=0:   GET /orders?since=last_check -> []
t=30s: GET /orders?since=last_check -> []
t=60s: GET /orders?since=last_check -> [{ new order }]

Webhooks: The external service calls your application when something changes.

t=47s: POST /webhooks/orders { new order data }

When Polling Makes Sense

• The source doesn't support webhooks. If this is the case, polling is your only option.
• You need consistency guarantees. Webhooks can fail or arrive out of order. Polling against the canonical API gives you a guaranteed, complete view of state.
• Low change frequency with predictable patterns. A nightly sync job is simpler than webhook infrastructure.
• Cursor-based event streams. APIs like Stripe's Events API are designed to be polled forward.

When Webhooks Win

• Near real-time is required. Polling at 60s intervals means up to 59 seconds of latency. Webhooks are sub-second.
• High event volume. Polling at sufficient resolution for high-frequency events is expensive. Webhooks cost one call per event.
• The source supports them. Stripe, GitHub, Shopify, and most major services offer webhooks — use them.
• You need to react, not reconcile. "When X happens, do Y" fits webhooks naturally.

The Latency Math

With polling every N seconds: worst-case latency = N seconds, average = N/2 seconds. To achieve sub-second latency you'd need to poll every second — 86,400 API calls per day, likely rate-limited.

The Cost Math

1,000 events/day spread across 24 hours:

• Polling every 60s: 1,440 API calls — 440 wasted on empty responses
• Polling every 10s: 8,640 API calls — 7,640 wasted
• Webhooks: 1,000 HTTP requests — zero wasted

Reliability Trade-offs

Polling advantage: If your server is down, you don't miss events — just query again. The API is the source of truth.

Webhook advantage: Zero wasted calls, events arrive immediately.

Webhook risk: If your endpoint is down when an event fires, you may miss it. This narrows significantly with retry logic, delivery logs, and replay capability.

When to Use Both

Use webhooks as your primary mechanism (speed and efficiency), with periodic polling as a reconciliation check:

Every event:  Process via webhook (fast path)
Every hour:   Poll for events since last reconcile (safety net)

This gives you webhook latency with polling's completeness guarantee.

Decision Guide

Question	Use
Source supports webhooks?	Yes → webhooks
Sub-minute latency needed?	Yes → webhooks
Event frequency high (>100/day)?	Yes → webhooks
Guaranteed completeness needed?	Yes → polling or both
Simple scheduled sync?	Yes → polling
React to events in real time?	Yes → webhooks

---

Using webhooks? Bluejay Relay handles receipt, logging, retry, fan-out, and replay — so you don't have to build it yourself.