Oct 08, 2026 by Offer

What is an API (With Examples): Interview Answer Guide 2027

An API — Application Programming Interface — is a contract letting software components communicate without knowing each other's internals. A good api interview question answer explains REST concretely: resources at URLs, HTTP verbs (GET, POST, PUT, DELETE) as actions, status codes as results, and JSON as the message format — with one example request.

What the Api Interview Question Tests

Whether you can define an API without jargon: a contract between software, hiding implementation.
Whether you know REST mechanics: verbs, status codes, JSON payloads, statelessness.
Whether you can walk through a real example, e.g., GET /users/123 returning 200 with JSON.

How to Answer the API Interview Question

Walk through examples the way a client would experience them:

Example 1 — read. `GET /products/7` → `200 OK` + `{"id":7,"name":"Keyboard","price":79}`. Pure retrieval.
Example 2 — create. `POST /products` with body `{"name":"Mouse","price":29}` → `201 Created` + the new object's URL.
Example 3 — error. `GET /products/999` → `404 Not Found` + `{"error":"no such product"}`. The code, not the body, carries the meaning.
Example 4 — auth. `GET /me` without a token → `401 Unauthorized`. Real APIs gate access; mention it to show maturity.

Sample close: "Four calls cover the whole lifecycle: read, create, fail gracefully, and authenticate."

Common Mistakes With the Api Interview Question

Defining API as 'a way to get data' only — APIs also trigger actions and hide implementation, not just serve data.
Mixing up PUT and PATCH, or using GET for state-changing operations.
Ignoring status codes: returning 200 for everything hides errors from clients.

'What is an API' filters for communication skills as much as knowledge: everyone uses APIs, but strong candidates explain the contract idea and walk a request lifecycle crisply. Have your one example rehearsed.

Keep Reading

FAQ

What is an API in simple terms?

A defined way for software to request services from other software — like a menu: you order by name without knowing how the kitchen works.

What is a REST API?

An API style using HTTP: resources have URLs, verbs (GET/POST/PUT/DELETE) say what to do, and responses carry status codes plus data, usually JSON.

What is the difference between PUT and POST?

POST typically creates a new resource; PUT replaces a resource at a known URL idempotently — repeating it has the same effect.

What are common HTTP status codes?

200 OK, 201 Created, 400 Bad Request, 401 Unauthorized, 404 Not Found, 500 Internal Server Error. Codes tell the client what happened without reading the body.

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