When should a monolith be split into services, and what would you do first?
Answer it out loud before you open anything. The value of the flags below is in comparing them to what you actually said — including whether you named a cost, or only a principle.
The situation behind the question
A four-year-old monolith, one repository, one deployment, eighteen engineers on three teams. Deploys are blocked several times a week by unrelated failing tests. Leadership has asked for a microservices migration plan.
What it is really testing
Whether the candidate can identify the actual constraint. The stated pain is deployment coupling, and the interesting answer is that splitting the deployment does not require splitting the process — and that a team unable to keep module boundaries in one repository will not keep them across a network.