Scaled custom help desk software across 5 school districts. Way harder than it sounds when you realize that we needed a tunnel to get an external site working, complex routing to get the servers to communicate with one another without exposing one districts network to the others. And I also made it auto deploy on a successful CI test. The only thing that really perfectly worked on the first try was the database (CockroachDB). Everything else was a complete mess of DNS and routing rules.