Ordering and Out-of-Order Events

Why order is not guaranteed

It is tempting to assume webhooks arrive in the same order the events actually happened, but many systems make no such promise, and relying on one quietly is a recipe for bugs. Retries, parallel delivery workers, and ordinary network variability can all shuffle the sequence along the way. An updated event might land before the created event it logically follows, simply because the second delivery took a faster path.

If your processing silently assumes a strict order, these reorderings produce subtle and intermittent failures: a record updated before it appears to exist, a cancellation applied before the thing it is meant to cancel ever arrives. The safe stance is to treat ordering as best-effort at most, and to build logic that copes gracefully when the order turns out to be wrong, because eventually it will.

Which workflows care

Not every integration is actually sensitive to order, and it is worth knowing which of yours are. If each event is genuinely independent — a notification, a logged action, an audit entry — then the sequence may not matter at all, and you can process events freely as they arrive. Ordering only starts to bite when events describe transitions of the same entity, where the correct final state depends on applying the changes in the right sequence.

Spotting these order-sensitive cases early is half the battle won. Ask yourself a simple question for each flow: does processing event B incorrectly depend on whether event A came first? If the answer is yes, you need a deliberate strategy beyond hoping the network cooperates. If the answer is no, you can keep that handler simple and spend your effort elsewhere.

Reconcile with timestamps or versions

The common and reliable fix is to carry a version number or a timestamp in each event that describes the state of the underlying entity, and then to ignore any event that is older than what you have already applied. This way the newest information always wins, no matter the order in which the deliveries happen to reach you.

if (event.version <= record.version) {
  return respond(200); // stale, skip
}
applyEvent(event);
record.version = event.version;

With this guard in place, a late-arriving older event simply cannot overwrite newer data, because the version check rejects it before it does any harm. It is a small amount of code that eliminates an entire family of ordering bugs.

Think in states, not sequences

A durable mindset, beyond any single technique, is to treat each event as a statement about the world rather than a step that must follow the previous one. Where the provider allows it, prefer events that convey the full current state of the entity, so that applying the latest one is correct even if you happened to miss some earlier events entirely. That framing makes whole classes of ordering problems melt away.

When you truly do need strict ordering and cannot get it from the stream alone, a periodic reconciliation against authoritative state closes the remaining gaps, much as described in replaying missed events. Whether a given provider's events carry version fields you can rely on is documented in the API documentation.