Webhook or polling: how one system learns that something changed in another

If the other system can notify you, use a webhook: it arrives at once and wastes no requests. If it cannot, or if you cannot risk missing a notice, poll. The most robust setup combines the two. It is the question behind “how do I know the customer paid”, “how do I receive the messages” or “how do I know the order changed”.

The two ideas

With polling, your system asks every so often, “anything new?”. You are the one asking, at the pace you choose. With a webhook, it is the other system that calls you: when something happens, it makes an HTTPS request to an address of yours and hands over the data. It does the notifying, at the moment of the event.

Side by side

Criterion Polling Webhook
Speed Delayed until the next interval. Almost immediate.
Waste Many requests that answer “nothing new”. A request only when something happens.
What you need on your side A scheduled task. No public address needed. A public HTTPS address that is always answering.
If your server is down Catches what it missed on the next poll. May lose the notice. Services usually retry, but only for a limited time.
Security You control the connection you make. You must confirm the notice really came from who it says.
Simplicity Very simple. A little more care.

When to use each

1 Use a webhook for payments, incoming messages and orders, where waiting minutes costs you. See webhooks from Meta: verifying and receiving.
2 Use polling when the other side has no webhooks, when you only want an hourly report, or when you have no public address to receive on. It is what a scheduled task does. See cron jobs.
3 Combine them when missing a notice is costly: the webhook handles the immediate side and a slow poll, say hourly, picks up what escaped.
4 In n8n, the Webhook trigger matches the first case and the Schedule Trigger the second. See n8n Schedule Trigger or a cron job.

What a well-made webhook does

1 Answers quickly with a success code, and only then does the heavy work.
2 Confirms where the request came from, normally through a signature. See receiving a webhook in PHP and checking its signature.
3 Copes with the same notice twice: services may resend, and you must not record the same payment twice.
4 Logs what it receives, so you know what happened when something fails.
In n8n, the test webhook and the production webhook are different addresses. The test one only answers while it is listening in the editor. The production one only answers with the workflow active. Putting the test address into an outside service is the most common cause of “the webhook does not fire”.
So that notices are not lost, store them before processing. A notice that arrives and fails halfway can be picked up again if it was stored; if not, it is gone.

Connecting two systems and not sure which route to use? Tell us what they need to say to each other.

Open a support ticket

SEE ALSO

Receiving a webhook in PHP and checking its signature

n8n Schedule Trigger or a cron job: which to use

Cron jobs: what they are for and how to create one

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