Mobile apps rarely work in isolation. Most production apps at companies like Spotify or Uber rely on backend services for authentication, user data, content, and business logic.
Explain the role of REST APIs in mobile apps. In your answer, address these points:
The interviewer expects a practical systems explanation rather than protocol trivia. You should describe how REST fits into a typical mobile architecture, what benefits it provides, and what trade-offs or limitations engineers should understand when building or consuming these APIs.
REST APIs separate the mobile client from backend services. The app focuses on presentation and user interaction, while the server owns shared data, business rules, and persistence.
REST models data as resources exposed through endpoints such as /users/123 or /orders/42. Mobile apps interact with these resources using standard HTTP methods like GET, POST, PUT, PATCH, and DELETE.
GET /api/v1/profile
Authorization: Bearer <token>
Each REST request should contain all information needed to process it, such as authentication tokens and request parameters. This makes backend services easier to scale because servers do not need to keep per-client session state in memory.
Mobile apps commonly send and receive JSON because it is lightweight, human-readable, and easy to parse across platforms. The API defines a contract so both client and server agree on field names, types, and response structure.
{ "id": 123, "name": "Ava", "premium": true }
In real systems, REST APIs must handle authentication, retries, timeouts, pagination, caching, and versioning. These concerns are critical on mobile because networks are unreliable and devices have limited battery and bandwidth.
