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REST Interview Questions & Answers- Part 6
Every modern mobile app relies on APIs to function. Whether it’s pulling data from a server, sending user input, or syncing with third-party services, REST APIs make it all possible. If you’re a mobile developer—working with Android, iOS, Flutter, or React Native—knowing how to handle RESTful communication is essential.
This page provides practical REST API interview questions and answers to help you prepare for roles where server communication is key. You’ll review topics like JSON formatting, HTTP methods, latency handling, error messages, and API integration best practices. These questions will also help you show employers that you can build responsive, data-driven apps that users love.
Whether you’re fetching product details in an eCommerce app or updating user profiles in a fitness tracker, REST APIs are behind the scenes. Study this guide to confidently discuss how your mobile apps interact with APIs in real-world scenarios.
Answer:
To secure a RESTful API, several measures must be implemented, including:
- Authentication and Authorization: Implement mechanisms to authenticate users and ensure they have the appropriate permissions to access resources.
- 2. HTTPS Encryption: Use HTTPS to encrypt data in transit, safeguarding it from eavesdropping and tampering.
- Input Validation: Validate input data to prevent security vulnerabilities like injection attacks and cross-site scripting (XSS).
Answer:
Different authentication methods employed in RESTful web services encompass basic authentication, token-based authentication, and OAuth.
Answer:
Token-based authentication is a method of verifying users by exchanging a token for a set of permissions. After a user logs in, the server issues a token, which is stored on the client side. Subsequent requests from the client include this token, allowing access to protected resources.
Answer:
CORS (Cross-Origin Resource Sharing) is a browser security mechanism restricting cross-domain requests. To enable CORS in RESTful web services:
- Set the Access-Control-Allow-Origin header in the response to specify allowed domains.
- Optionally, configure other headers like Access-Control-Allow-Methods and Access-Control-Allow-Headers to restrict permitted HTTP methods and headers for cross-origin requests.
Answer:
A PUT request updates an entire resource on the server and requires the entire resource in the request body. If the resource exists, it replaces the resource entirely, and PUT requests are idempotent. Conversely, a PATCH request updates part of a resource on the server, necessitating only the changes in the request body. It updates only specified fields if the resource exists, and PATCH requests are not idempotent.
Answer:
Rate limiting in RESTful web services restricts the number of requests a client can make within a specific time frame. This helps prevent API abuse by limiting the volume of requests made by a single client, ensuring fair and responsible usage.
Answer:
Implementing rate limiting can be achieved using various methods, including:
- Utilizing middleware or libraries with rate-limiting capabilities.
- Employing a reverse proxy or API gateway that supports rate limiting.
- Manually implementing rate limiting logic in the application code.
Answer:
API throttling is similar to rate limiting, as it restricts the rate at which a single client or user can access an API. This mechanism safeguards against API abuse by controlling the number of requests a client can make within a specified timeframe. API throttling can be used in conjunction with rate limiting to enhance protection.
Answer:
Load balancing involves distributing incoming network traffic across multiple servers or instances. This strategy enhances the availability, scalability, and reliability of web applications and APIs. Various load balancing techniques, such as round-robin, least connections, IP hash, and session persistence, can be employed to achieve efficient distribution of traffic.
Answer:
Load balancing within RESTful web services can be implemented through various means, including:
- Utilizing load balancer appliances or software designed for this purpose.
- Leveraging cloud-based load balancer services provided by cloud providers.
- Manually implementing load balancing logic directly within the application code.
Answer:
Service discovery is the process of automatically identifying and registering network services within a distributed system. It simplifies the management and scalability of microservices and containerized applications. Service discovery can be achieved through techniques such as DNS-based discovery, client-side discovery, and server-side discovery.
Answer:
An API gateway serves as a reverse proxy and acts as the primary entry point for a set of microservices or APIs. It streamlines the architecture, management, and security of a distributed system. API gateways handle various tasks, including routing requests, load balancing, rate limiting, authentication, and monitoring, providing a centralized point for managing API-related functionality.
Answer:
A DELETE request is used for deleting a resource on the server, with the response body being optional. A successful DELETE request removes the resource from the server, but DELETE requests are not idempotent, meaning multiple identical requests may have different outcomes. In contrast, a HEAD request is employed for retrieving metadata about a resource on the server, with the response body not included. A successful HEAD request results in the server returning metadata about the requested resource, and HEAD requests are idempotent, allowing multiple identical requests without changing the server’s state.
Answer:
A reverse proxy is a server positioned between clients and a set of servers, forwarding client requests to the appropriate server. In contrast, an API gateway is a specialized type of reverse proxy specifically designed to manage API traffic. It offers additional features such as routing, load balancing, and security for APIs, making it more tailored to the needs of modern microservices and APIs.
Answer:
Implementing token-based authentication in RESTful web services involves the generation and issuance of tokens by the server, validation of tokens on subsequent requests, and enforcing authorization based on the permissions granted by the token.
Answer:
JWT, or JSON Web Token, is a format used for encoding tokens as JSON objects. In RESTful web services, JWTs are commonly employed for authentication and authorization purposes. These tokens include a set of claims, such as user identification and expiration time, which are digitally signed with a secret key to ensure integrity and prevent tampering.
Answer:
OAuth is an authorization framework that enables third-party applications to access protected resources on behalf of a user. In the context of RESTful web services, OAuth is frequently utilized for user authentication and the issuance of access tokens. These access tokens are then used to gain access to protected resources, allowing third-party applications to interact securely with user data and APIs.
Answer:
A query parameter is used for filtering and sorting data, appearing after the “?” in the URL. It’s not required for the URL to function and can be optional. Meanwhile, a path parameter is used to identify a specific resource, forming part of the URL path. It’s required for the URL to function and must be included in the URL.
Answer:
Authentication in a REST API is often handled using tokens, API keys, or other authentication mechanisms. Authorization is managed through role-based access control (RBAC) or similar authorization mechanisms, where users or clients are granted specific permissions to access resources based on their roles or attributes.
Answer:
Versioning in RESTful APIs can be achieved through various approaches:
- URL Versioning: Include the version number in the URI path, such as “/v1/resource” and “/v2/resource.”
- Header Versioning: Include the version number in a custom header, like “Accept-Version: v1” or “API-Version: 2.”
- Media Type Versioning: Incorporate the version number into the media type of the response, like “application/vnd.myapi.v1+json.”