The deprecation warning sat in our logs every single day for eleven months. I probably read it four hundred times, and every time I thought “yeah, we should fix that” and moved on with my day. (You can guess how this ends.)
The Scene
We run a fairly boring internal service that handles billing webhooks. It talks to an old payments library, version 2.x, the kind of thing nobody wanted to touch because it worked. In March 2025 the vendor started logging a deprecation notice: the verifySignature() method we used was being replaced by verifySignatureV2(). Nothing broke. The old endpoint was still up. So we filed a ticket, marked it P3, and forgot about it. The next eleven months, though, are on me.
The Spiral
Fast forward to August. Tuesday afternoon, our support channel lights up: payments are failing for maybe a third of customers. Not all of them, which is the worst possible version of this problem, because it looks like a data issue instead of an obvious outage. Still with me? So I checked the usual suspects first. Database, fine. Network, fine. The vendor’s status page, green, of course.
It took me about forty minutes to stop poking dashboards and actually grep the logs. There it was, mixed in with a thousand warnings I’d learned to scroll past: 400 Bad Request: signature verification failed.
The Discovery
The provider had quietly killed the old endpoint two weeks earlier. Our requests only still worked for customers whose signatures happened to pass the new format. That’s why it was partial, and why no status page ever turned red for us.
The fix itself took maybe twenty minutes. Swap the method call, run the test suite, deploy. What stung was rereading that same deprecation warning, dated March, and realizing I had personally decided eleven times that it wasn’t urgent.
The Lesson
- Deprecation warnings have an expiry date, sort of. Ours didn’t say when the old endpoint dies, so my brain filed it under “someday.” I should have just asked the vendor for the cutoff date.
- Partial failures hide longer than total ones. If every payment had failed at once we’d have caught it in ten minutes. The slow bleed bought the bug a whole afternoon of my life and cost a few customers some real frustration.
- A P3 ticket with no date is a wish, not a plan. “We’ll get to it” is not a deadline.
What I’d Do Different
- Treat any deprecation notice from a payment or auth vendor as a dated work item, with a real deadline, even if the deadline is just “next sprint.”
- Ask the vendor when the old path goes away. If they can’t give a date, that itself is information and probably means migrate sooner.
- Alert on deprecation warnings in production logs instead of letting them pile up as background noise.
Final Thoughts
The annoying part is that the fix was one line and I’d known about it since spring. Eleven months of “we should really do that” for twenty minutes of actual work. So yeah, I read my deprecation warnings properly now, and it took a partial outage to teach me that.