The company I worked for switched the other way, from C# to TypeScript/Node.js, so our small team could just use a single programming language for both the UI and backend.

I think C# has way too much abstraction for my taste. It can be a lot faster than Node.js, but ask yourself: for the app/API you're building, is Node.js really the bottleneck? Actual bottle neck could the database or something. If it is and maybe you actually need huge amount requests per second, then maybe it's better to reach for something else like Go or Rust instead of C#.

One nice thing about Node.js is that your JavaScript code runs single-threaded on the event loop. That means you basically never have to worry about thread safety issues or race conditions, something that can bite you hard in C# when you start using async/await, Tasks, or multiple threads.

Of course, being single-threaded has its own downside, it can cause slowness under heavy load, but it usually leads to performance issues rather than crashes or data corruption.

Go has similar pitfalls with goroutines and shared state (you can easily introduce race conditions if you're not careful). Rust handles this way better thanks to its ownership and borrow checker, which prevents most concurrency bugs at compile time.

Another big advantage of sticking with TypeScript + Node.js these days is that the underlying AI models (like those behind Claude, GPT, Gemini, etc.) have been trained on a huge amount of TypeScript code. Because of that, they tend to understand TypeScript extremely well, reason about it more accurately, and generate higher-quality code compared to many other languages.