The verdict in three sentences
A missed webhook turns a paid order into an angry customer: the money left, the order was never marked. Raw failure rates run 1 to 5% depending on network and endpoint quality. With verified signatures, idempotency, exponential retry and a polling fallback, you drop below 0.1% loss.
The five lines of defence
A reliable webhook is not one function, it is a chain. Each link catches the previous one.
| Defence | Role | Effect on loss rate |
|---|---|---|
| HMAC signature | Reject forged calls | Security, no fraud |
| Idempotency key | Process once even if received 2x | Zero double fulfilment |
| Exponential retry | Replay if endpoint is down | -70 to -90% failures |
| Dead-letter queue | Isolate stuck events | No silent loss |
| getStatus polling | Recover never-received webhooks | Under 0.1% |
None of these defences is optional in production.
The retry schedule
An endpoint may be down 30 seconds or 10 minutes. Retry must be patient without hammering. Recommended orders of magnitude.
| Attempt | Delay after previous | Cumulative |
|---|---|---|
| 1 (immediate) | 0 s | 0 s |
| 2 | 30 s | 30 s |
| 3 | 2 min | ~2.5 min |
| 4 | 10 min | ~12.5 min |
| 5 | 1 h | ~1 h 12 |
| 6 (final) | 6 h | ~7 h |
After the last attempt, the event goes to a *dead-letter queue* for manual handling or replay. A managed queue costs roughly USD 10-40/month by volume, negligible next to a single lost order.
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Mini case study
Amara runs a delivery platform in Accra with about 3,000 payments/month. Before hardening, his webhook failure rate was 4%, i.e. 120 orders/month paid but stuck, at an average basket of GHS 90: GHS 10,800 in disputed revenue and an overloaded support desk. After adding idempotency, retry and polling every 15 minutes, the rate fell to 0.08%, i.e. 2-3 orders/month recovered by hand. Setup cost: about USD 800, paid back in under a month.
FAQ
Why does my webhook fail sometimes? Unstable network, momentarily unavailable endpoint, timeout, or load spike. That is why raw failure rates of 1 to 5% appear without a recovery mechanism.
What is the idempotency key for? To fulfil an order only once even if the webhook arrives two or three times. Without it, the customer can be double-charged or double-served.
Is retry enough? No. Retry recovers downed endpoints, but if the provider never sent the webhook, only a getStatus polling fallback closes the gap.
What is a dead-letter queue? A queue where events land when the system could not process them after all retries, for manual replay without ever losing the information.
What reliability target should I aim for? Under 0.1% loss on payment confirmations. It is achievable with the five defences combined.
Let's talk about your project. We harden your mobile money webhooks with signature, idempotency, retry and a polling fallback to target under 0.1% loss. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
