I'm on a team that is working to build "long lived" software. We are in the beginning phase so there is a lot of changes (we've gone from C# applications to now

I'm on a team that is working to build "long lived" software. We are in the beginning phase so there is a lot of changes (we've gone from C# applications to now a micro service architecture using Web API) but once we get a stable backing it shouldn't change. The platform is for handling Medicaid visits for patients of our clients (I work for a third party administrator for health care). The goal is to architect it to be extensible for each new client onboarded and then just be done with it (save for updating .NET versions when needed).