APIs and RESTful API Design Concepts for Software Engineering Interviews Quiz

This quiz challenges your understanding of fundamental APIs and RESTful API design principles frequently tested in software engineering interviews. Explore key concepts, HTTP methods, status codes, best practices, and common pitfalls related to RESTful architecture.

1. Definition of an API

   Which statement best describes an API in software engineering?

   1. An API is an interface that allows different software applications to communicate with one another.
   2. An API is a programming language used to write backend code.
   3. An API is a type of database used to store application data.
   4. An API is hardware used to connect multiple computers.

   Explanation: An API provides defined methods for different systems to interact, making communication between software components possible. It is not a programming language, which is used to develop software, nor is it a database, which stores data. Additionally, APIs are not hardware but are part of the software infrastructure.

2. RESTful Architecture Principle

   In a RESTful API, what does 'statelessness' mean in the context of client-server communication?

   1. Each request from a client contains all necessary information for the server to understand and process it.
   2. The server maintains a session history for each client.
   3. The client stores partial copies of server data between requests.
   4. Requests must occur in a fixed sequence during a session.

   Explanation: A stateless RESTful API does not store client context between requests; every request must provide all information required for processing. The server does not keep session history or require fixed sequences, and the client is not responsible for storing server state beyond caching responses.

3. HTTP Methods in REST

   Which HTTP method is commonly used in RESTful APIs to retrieve data without modifying it?

   1. GET
   2. POST
   3. DELETE
   4. PATCH

   Explanation: GET is used to retrieve or read data and should not cause side effects. POST typically creates resources, DELETE removes them, and PATCH applies partial modifications. Only GET fits the requirement of data retrieval without modification.

4. Resource Naming Best Practice

   According to RESTful design conventions, how should resource names typically be structured in URIs?

   1. In plural nouns, such as /users or /orders
   2. As verbs representing actions, such as /getUser
   3. With random alphanumeric strings for uniqueness
   4. As capitalized words for better readability

   Explanation: RESTful best practices use plural nouns to represent resource collections, making the API intuitive and consistent. Using verbs mixes implementation with resource description, random strings reduce clarity, and capitalization is not standard and may cause inconsistency.

5. Correct Use of HTTP Status Codes

   What HTTP status code should a RESTful API return after successfully creating a new resource?

   1. 201
   2. 200
   3. 404
   4. 500

   Explanation: A 201 status code indicates a resource was successfully created, which is the expected response after a successful POST. A 200 indicates a general success but not specifically creation, 404 means not found, and 500 indicates a server error.

6. Idempotency in HTTP Methods

   Which HTTP method is idempotent, meaning multiple identical requests have the same effect as a single one?

   1. PUT
   2. POST
   3. CONNECT
   4. TRACE

   Explanation: PUT requests are idempotent since repeated requests with the same data will always produce the same result. POST is not idempotent because it usually creates new resources on each call; CONNECT and TRACE have other purposes and are not typically used for resource modification in REST APIs.

7. Handling Non-existent Resources

   Which status code is most appropriate when a client requests a resource that does not exist in the server?

   1. 404
   2. 401
   3. 503
   4. 301

   Explanation: A 404 status code clearly indicates that the requested resource could not be found. A 401 signals unauthorized access, 503 means the service is unavailable, and 301 is used for permanent redirection, none of which fits this scenario.

8. Purpose of the PATCH Method

   When should the PATCH HTTP method be used in a RESTful API?

   1. To partially update a resource with provided changes
   2. To completely replace a resource with new data
   3. To fetch a list of resources
   4. To remove a resource from a server

   Explanation: PATCH is intended for partial updates, sending only the changes instead of the entire resource. PUT replaces the whole resource, GET fetches resources, and DELETE removes them—all different from PATCH’s partial update role.

9. Versioning an API

   How is API versioning commonly achieved in RESTful APIs to ensure backward compatibility?

   1. By including the version number in the URI, such as /v1/resources
   2. By using only query parameters to indicate version
   3. By keeping a single version and updating resources in place
   4. By not allowing any version information in the API

   Explanation: Putting the version in the URI is a widely accepted convention for clear version management. Query parameters are less explicit; updating resources in place risks breaking clients, and omitting versioning removes compatibility guarantees.

10. RESTful API Response Format

    Which data format is most commonly used in RESTful API responses today for readability and compatibility?

    1. JSON
    2. XML
    3. CSV
    4. YAML

    Explanation: JSON is currently the most popular for RESTful APIs due to its readability and ease of use with most programming languages. XML was more common previously, while CSV and YAML are less standardized choices for REST responses.

11. Query Parameters Usage

    For which scenario are query parameters typically used in RESTful APIs?

    1. To filter results or provide optional modifications, such as GET /users?age=21
    2. To define the main resource’s unique identity in the path
    3. To send request payload in the body of the request
    4. To specify the content type of responses

    Explanation: Query parameters modify or filter a GET request, as with filtering users by age. Path variables identify primary resources, the body contains request data, and headers (not query parameters) specify content types.

12. Security Best Practices

    What is a common security practice to protect RESTful APIs from unauthorized access?

    1. Including authentication tokens or API keys with each request
    2. Allowing unrestricted public access for ease of use
    3. Encoding credentials only in the URI path
    4. Avoiding authentication to improve performance

    Explanation: Authentication tokens or API keys verify the client’s identity and secure the API. Leaving the API entirely open or encoding credentials in the URI is risky. Skipping authentication undermines security and exposes systems to attacks.

13. Handling Large Resource Lists

    What is pagination and why is it used in RESTful APIs when returning large lists of resources?

    1. It divides large lists into smaller parts to limit the number of results returned per request.
    2. It sends all results at once regardless of size.
    3. It automatically deletes extra resources to keep lists short.
    4. It encrypts list responses for security.

    Explanation: Pagination splits big datasets into small sections, improving performance and usability. Sending all results may overload the client or network, while deleting or encrypting data does not address the issue of handling large lists.

14. Best Practice for Error Responses

    Which approach should a RESTful API take when returning an error to a client?

    1. Include a meaningful error message and appropriate HTTP status code in the response
    2. Return only a generic 200 status code regardless of the problem
    3. Send an empty message body with no status code
    4. Return unrelated error information from other endpoints

    Explanation: Combining HTTP status codes with informative error messages helps clients understand and respond to issues correctly. A 200 indicates success, not errors; empty bodies or unrelated information do not assist debugging or usage.

15. API Documentation Importance

    Why is maintaining clear and accurate documentation important for a RESTful API?

    1. It helps developers understand and correctly use the API endpoints and data formats.
    2. Documentation should be hidden to prevent unauthorized usage.
    3. Documentation is only needed for internal testing, not end users.
    4. Accurate documentation is not necessary if the API has few endpoints.

    Explanation: Clear documentation enables developers to integrate efficiently and correctly, reducing errors. Hiding documentation or limiting its scope creates usability problems, and even simple APIs benefit from accurate documentation.

16. API Rate Limiting

    What is the main purpose of API rate limiting in RESTful APIs?

    1. To prevent clients from making too many requests in a short period and protect resources.
    2. To permanently block all traffic from certain users.
    3. To increase the size of response payloads for each request.
    4. To randomly throttle different HTTP status codes.

    Explanation: Rate limiting keeps systems safe from abuse and overload by restricting request rates. Blocking all users, increasing payload sizes, or changing status codes arbitrarily do not address request volume and can harm usability.