JSON in REST APIs — Interview Questions
⚡ Short Answer
In REST, JSON is the standard body format for both requests and responses. Clients send data as a JSON body with Content-Type: application/json (and Accept: application/json to ask for JSON back); the server parses it, does the work, and returns a JSON body plus the right status code. It's the common language between client and server.
☕Coffee Chat Question
Concept Made Simple
“How is JSON used in REST APIs?”
🧠Mind Map Answer
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⌨️Hands-on Keyboard
Learn by Doing
POST /api/users HTTP/1.1
Content-Type: application/json
Accept: application/json
{ "name": "Guru", "email": "guru@example.com" }
HTTP/1.1 201 Created
Content-Type: application/json
{ "id": 101, "name": "Guru" }🔥What If?
Think Beyond the Expected
What happens if you POST JSON without a Content-Type: application/json header?
The server may not know to parse the body as JSON — many frameworks only run the JSON body parser when Content-Type is application/json, so req.body ends up empty or a raw string. Always set the header; a mismatched or missing Content-Type is a very common 'why is my body undefined?' bug.
😂Real World
This is the backbone of virtually every web/mobile app: the client GETs JSON to render, POSTs JSON forms, and the server returns JSON. The Content-Type/Accept headers are what make the exchange unambiguous.
🎯Interviewer's Expectation
Keywords they're listening for:
⚠️Common Mistakes
- ✗Omitting Content-Type: application/json
- ✗Ignoring the Accept header
- ✗Returning 200 for an error with an error body
✅Best Practices
- ✓Always set Content-Type and Accept
- ✓Return correct status codes with JSON bodies
- ✓Keep request/response shapes documented
🔁Follow-up Questions
- 1What's the difference between request and response JSON?
- 2Which status codes pair with JSON error bodies?
- 3How does content negotiation work?
🧩Related Technologies
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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 is JSON used in REST APIs?" 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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