Ask HN: Do you have examples of (very) convoluted APIs?

I once contemplated an API where I would convert audio into a video, upload it to YouTube, let their Content ID detection run and then get their detected artist(s) as output, probably hours or days later. A very convoluted Shazam :-)

Do you have other examples of real APIs where lots of weird, slow, unexpected complex stuff is/was happening in the background, in order to provide the API response?