How do you distinguish 400, 401, 403, and 404?
PICTURE THIS: 1, 2, 2, 8
Simple meaning
400 is a bad request: malformed JSON or failed validation.
WHY — HTTP instead of guessing?
Why interviewers care about HTTP:
question about HTTP.
trade-offs, and what you would actually do on a Backend project - not buzzwords.
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:
- 1400 is a bad
request: malformed JSON or failed validation.
- 2401 means the caller
is not authenticated.
- 3403 means the caller
is authenticated but not allowed.
- 4404 means the resource
is missing, or you hide its existence for security.
- 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
400 is a bad request: malformed JSON or failed validation. 401 means the caller is not authenticated.