User Reuploaded. Still Saw the Old Image.

We had a weird bug in prod. User reuploaded a car image… but still saw the old one. 👻

The flow was simple:

1. User uploads an image
2. We send it to a third-party AI service for processing
3. Service fires a webhook → we store the result

Then this happened:

• User uploads Image A → not happy → reuploads Image B
• Image B finishes processing first ✅ — we store it
• Image A finishes late 💀 — overwrites Image B

Classic race condition.

The root cause: webhook delivery timing is completely unpredictable. Sometimes seconds. Sometimes minutes. Order of uploads ≠ order of webhook arrival.

The fix: version every upload

Each upload request gets a version number. When the webhook arrives, we check:

if (webhook.version < stored.latestVersion) {
    // stale response — discard
    return;
}
// latest — store it
storeImage(webhook.result);

• Latest version? Store it ✅
• Older version? Discard it 🗑️

One version check. That’s it. Users now see consistent data.

You could also use request timestamps — only accept the webhook if it’s newer than what’s stored. Works too, but version numbers are safer since timestamps can drift across servers.

Distributed systems are fun… until time starts lying to you. 😄