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Concurrency or Parallelism?
What is the difference between concurrency and parallelism, and can you have one without the other?
The scenario
A team's image-processing endpoint is slow. Someone proposes marking the handlers
async "so they run in parallel". The service is Node.js, the work is a 300ms synchronous resize, and the box has eight cores.What it tests
- Whether the candidate separates a structural property (tasks overlap in progress) from a physical one (instructions execute at the same instant)
- Whether they can give a concrete example of each in isolation, not just a definition
- Whether they understand that the distinction changes what you build, not just what you call it
Answer it out loud first. Recognising a good answer is not the same skill as producing one.