I'm a compulsive project hoarder and they all build on top of each other.
My first project was an open source full stack real-time framework I built about 10 years ago. I worked on it for about a year but it didn't get any traction so I pulled out some of the core logic and turned it into a stand-alone real-time remote event library; then within a few years, it got some traction. Then as WebSockets was becoming mainstream, I migrated my framework from HTTP long-polling to WebSockets but realized that it didn't add much value anymore, so I added pub/sub and RPC functionality to it (I also built some additional components so that it would run as a self-sharding cluster on Kubernetes).<p>Then I was working in the blockchain space and so I decided to build a lightweight quantum-resistant blockchain using my pub/sub library for peer-to-peer messaging... Then after I finished the blockchain, I decided that it would be fun to build a decentralized exchange on top of it and so I did. It's been running for a few years without issues though it's low volume but the community around it is dedicated.<p>Now I'm looking for new things which I could build on top of the blockchain and DEX. I'm thinking to use it as a payment system which accepts multiple cryptocurrencies interchangeably. I have a few ideas but I'm more focused on earning money nowadays so I'm hesitant to start anything new. Lol. After all that work, I only earn about $1000 per month in passive income. I'm a brute-force entrepreneur.<p>It's pretty easy to maintain all this. Like the author says; tests help, but even more important is to keep the number of third-party dependencies to a minimum and to avoid using overly niche programming features or features which are unlikely to be forward-compatible.