I was at first rushing implementing ~50 business rules (which changed weekly) on the setup of a system. Then this functional wise kid came along and we did in one week what took me 5 weeks.

Along with that, using MQTT to separate your program with Protobuf makes everything so much easier. Program crashes? Let it burn and let systemd restart it. So much easier to test too. Our code coverage is 99% if we exclude the main files that initialize everything.