Backend
Middleware
Code that runs in between a request coming in and the final response going out — commonly used for things like authentication checks, logging, or error handling.
Think of it like
Like a security checkpoint every visitor passes through between the front door and the meeting room — checking ID and logging the visit before letting them through.
Junior or senior?
Junior sounds like
Only knows a framework's built-in auth middleware.
Senior sounds like
Can name a custom middleware they wrote themselves and the problem it solved.
Ask them
“Tell me about a custom middleware you wrote. What did it do, and where did it sit in the request chain?”