My side project is about market making in a very particular way / or niched between decentralised exchanges and centralised one. The good thing is that this industry is so big that even as a small competitor I can do a lot. I don't have a product, just a basic page that's broken here and there https://asset.plus/ , my actual revenue comes from my bots trading. I am currently expanding my infrastructure, but I really have to take care of costs because servers for low latency are expensive.