Absolutely build that separate service. We run ours on a tiny server that does nothing but check signatures and push valid events into a persistent queue. That way, our main billing app can go down for an hour and we never drop a single update. It adds a step, but it makes the whole system boring and reliable, which is what you want with money.

That timing belt job taking all day, was the guy a trainee or a master tech?

Spot on from @evakelly, it's always the cheap part you ignore that fails first, like a phone charger cable.

I spent three days last year trying to fix a weird issue with my home server. I finally posted on a tech forum and a guy in Australia had it solved in an hour. It really changed how I work now.

Your tent story shows how we stick with old tools long after better ones come along.