EasyExperience level: 0-2 years · 3-5 years2 min read

HTTP Status Codes with JSON — Interview Questions

Reviewed by Gurusankar M.

Asked inAmazonMicrosoftDeloitteAccenture
#json#http status codes#error handling#rest#api design
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Short Answer

The status code carries the outcome (2xx success, 4xx client error, 5xx server error) and the JSON body carries the detail. Success bodies hold the resource; error bodies hold a consistent error shape (code, message, maybe field errors). Anti-pattern: returning 200 with {"error":...} — clients then can't rely on the status code.

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Concept Made Simple

Coffee Chat Question

“How do HTTP status codes work together with JSON responses?”

Remember It Faster

Mind Map Answer

2xx + JSON
resource / result body
400/422 + JSON
validation error details
401/403 + JSON
auth error message
5xx + JSON
generic error (no internals)

Keep one consistent error envelope across the whole API so clients parse errors the same way everywhere.

Learn by Doing

Hands-on Keyboard

http
HTTP/1.1 422 Unprocessable Entity
Content-Type: application/json

{
  "error": "validation_failed",
  "message": "Email is invalid",
  "fields": { "email": "must be a valid email" }
}

Think Beyond the Expected

What If?

Why is returning HTTP 200 with an error body considered a bad practice?

It breaks the contract clients, proxies, caches, and monitoring rely on. Tooling treats 2xx as success, so a 200 'error' won't trigger retries, alerts, or error handling — the failure hides. Use the correct 4xx/5xx status AND a JSON error body: the code for machines, the body for humans/details.

Real World

Mature APIs define one error envelope (code, message, requestId) and always pair it with the right status. Front-ends branch on res.ok/status; observability tools alert on 5xx rates — all of which relies on honest status codes.

Interviewer's Expectation

Keywords they're listening for:

  • status = outcome, body = detail
  • 2xx/4xx/5xx families
  • consistent error envelope
  • don't return 200 for errors
  • hide internals in 5xx

Common Mistakes

  • Returning 200 for failures
  • Inconsistent error shapes across endpoints
  • Leaking stack traces in 5xx bodies

Best Practices

  • Match status code to the real outcome
  • Standardize one error envelope
  • Return generic 5xx bodies (no internals)

Follow-up Questions

  1. What's the difference between 400 and 422?
  2. How do you design a consistent error schema?
  3. Which errors should be retried by clients?

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Plain-language foundations

I'm preparing for a software engineering interview and want to understand this from scratch, as a beginner.

Topic: REST APIs (JSON)
Interview question: "How do HTTP status codes work together with JSON responses?"

Please:
1. Explain the core idea in simple, plain language, using an everyday analogy.
2. Define any technical terms you use.
3. Walk through one small, concrete example.
4. Finish with a single sentence I can easily remember.

Keep the tone friendly and assume I'm new to this topic.
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