Okay, so I'm developing a system for a global rent-a-car broker. Basically website + a bunch of third party APIs + analytics, it's been running in production for over 4 years now.

Anyway, we had to connect our system to an external rental insurance API, nothing too complicated, got it to production in a month and it seemed to work okay, except the insurance provider claimed they're not getting any analytics data, which was weird, because there were no errors with API calls, and customers had no problem with the insurance.

After going back and forth for a month, we finally figured what's going on: after each API request, the insurance provider expected us to send the exact same data to their analytics API, because for whatever dumb reason they were unable to internally log requests in their analytics database.

tl;dr: we're doing 2 API calls with the exact same data to different endpoints, because a large rent-a-car insurance provider can't log their own analytics data.