What is middleware in Express used for?
PICTURE THIS: HOW TO EXPLAIN IT
Simple meaning
Functions that run before the route handler for logging, auth, parsing, and errors.
WHY — Node instead of guessing?
Why interviewers care about Node:
who only read docs from people who shipped.
and tied to Backend work.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1Functions that run before
the route handler for logging, auth, parsing, and errors.
- 2Why it exists
Order matters.
- 3I keep handlers thin
and push shared concerns to middleware.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
Functions that run before the route handler for logging, auth, parsing, and errors. Order matters.