Fedify: an ActivityPub server framework
Have you heard of Val Town? Val Town is a kind of code pastebin + serverless function.
Actually, #Fedify works just fine with Val Town. Here's a piece of ActivityPub software, implemented in about 170 lines of code, running on Val Town. Of course, it's built with Fedify!
Give it a follow @demo, and it will follow you back.
Curious to see how it was implemented? Check out the source code!