Payroll Engine: From Open-Source Prototype to Production-Ready

Two and a half years ago, I introduced Payroll Engine in this series — an open-source payroll calculation framework written in C#. The architecture was in place, regulation layers worked, the first Swiss payroll calculations were running. A working prototype. A lot has happened since. On the road to version 1.0, I had to answer the question every framework developer eventually faces: What's still missing between "it works" and "it's production-ready"? The answer was: quite a lot. Security as the Foundation A payroll system without robust security is not software — it's a liability. This was the area that demanded the biggest overhaul. Authentication and Authorization The backend now supports three configurable authentication modes: None — for local development and testing ApiKey — simple header-based authentication with environment variable fallback OAuth — full OAuth 2.0 integration with configurable authority, audience, and client secret On startup, the system validates the OAuth con