I guess having more languages works better if you have a microservice architecture. I tend to think of microservices as mostly good for solving organizational p

I guess having more languages works better if you have a microservice architecture. I tend to think of microservices as mostly good for solving organizational problems (namely, the need for everyone who works on a monolithic binary to agree on releases), and so don't prefer to use them if I don't have those problems. That said, I still don't really understand why you'd use TypeScript on the server at all if you need C# for other services; the advantages (faster builds?) don't seem sufficient to cover the costs of additional investment in tooling, inability to share common code, etc. (even assuming that training and/or cognitive-switching costs aren't an issue). Unless you're running the same code both on the server and in the browser; in that case I would probably dispense with C# but I could see someone choosing the three-different-languages approach, at least until .NET's in-browser story gets better. For a company with multiple unrelated projects, it'd be a judgment call, weighing the benefits of not being locked into a single ecosystem against the costs of losing economies of scale. I don't think I have a good general principle. I'm also not super clear on how well C# interoperates with C++; I've used both languages, but not together. The article makes it sound like it only "just works" if the entire API surface is C-compatible, which seems extremely limiting and not like something I would want to do regularly. In particular, it sounds like it'd be necessary to write wrappers on both ends, so that you have idiomatic C++ or C# everywhere except at the boundary. This is what I meant above about C++-to-Rust interop not being good enough yet—it works, but you have to go through C. Is this in fact what it's like, or can C# code automatically use C++ APIs that involve classes, RAII, templates, etc.? I don't advocate going all-in on C++ or Rust for a typical app, but rather having a setup that allows easily dropping into it in order to optimize hot paths. Performance tuning in a managed runtime is really hard and I prefer to avoid it.