General Motors Senior Software Engineer Interview Experience — Hiring Manager Chat Turned Technical, Then a Codility REST API Phone Screen

Earlier I had a call with the hiring manager. I expected the whole thing to be behavioral, but surprisingly it was almost entirely about technical decisions — things like how you'd go from a monolith to microservices, the tradeoffs between the two, and then how you'd go from microservices to a more modular architecture, and how to make those calls.

About a week after that call, a recruiter reached out to schedule the first-round technical phone screen.

It started with a Codility problem: implement a RESTful GET API, any language you want. The interviewer didn't ask me to actually run the code, just to walk through my approach — that took about 15 minutes.

The rest of the time was all knowledge questions, covering: idempotency, the N+1 problem in databases, changing an API's contract, service-level caching, what kind of monitoring you'd use to keep a service stable, how to use circuit breakers to avoid getting taken down by another service's failure, how to use rollbacks to handle a nasty production issue, and the CI/CD process in modern software development and how you'd implement it.