REST API -Top 50 interview questions

REST API

What is a REST API? Explain its key principles.

A REST API, or Representational State Transfer API, is a way for systems to communicate over the web using simple HTTP protocols. It’s like a set of rules that makes it easy for applications to exchange information.

Key principles of REST:

• Stateless: Each request is independent, so the server doesn’t store client data between calls.
• Client-Server Separation: The client takes care of the user interface, while the server handles data and logic.
• Cacheable: Responses can be cached to improve speed.
• Uniform Interface: It follows a consistent way to access resources using URLs.
• Layered System: You can add extra layers, like security or load balancers, without affecting how clients and servers interact.

How is REST different from SOAP?

REST and SOAP are both ways to build APIs, but they’re quite different:

What are the major HTTP methods used in RESTful services?

RESTful APIs let you interact with data on a server using simple HTTP methods. For example, you can use GET to fetch data, POST to add new data, PUT to update it, and DELETE to remove it. These methods make it easy to work with resources online.Here are the most common ones:

• GET: Fetches data (like reading a file).
• POST: Creates a new resource (like adding a new user).
• PUT: Updates an existing resource or creates it if it doesn’t exist.
• DELETE: Removes a resource.
• PATCH: Makes partial updates to a resource.

Explain the concept of statelessness in REST.

In REST, statelessness means the server doesn’t remember anything about the client between requests. Every request must include all the necessary information so the server can handle it.

Why is this helpful?

• It makes the system easier to scale because the server isn’t bogged down with session data.
• Clients can easily switch between servers without issues.

For example, if you request GET /products/123, the server doesn’t need to remember your previous interactions. It just processes this one request.

What is the difference between PUT and POST?

PUT and POST are both used to send data to the server, but they work differently:

What are the common status codes in REST API, and what do they signify?

HTTP status codes let the client know how the server handled the request. Here are some common ones:

• 200 OK: The request was successful.
• 201 Created: A new resource was created successfully.
• 400 Bad Request: The request was invalid or had missing data.
• 401 Unauthorized: You need to log in or provide valid credentials.
• 404 Not Found: The resource doesn’t exist.
• 500 Internal Server Error: Something went wrong on the server.

What is a resource in REST? Provide examples.

A resource is anything you can access via a REST API, like a piece of data or an object. Each resource is identified by a unique URL.

Examples:

• /users/1: Represents the user with ID 1.
• /products/101: Represents the product with ID 101.
• /orders/45/items: Represents the items in order 45.

Explain the term “Idempotency” in REST API with examples.

Idempotency means that making the same request multiple times will have the same result.

Examples:

• GET /users/123: Always fetches the same user data, no matter how many times you call it.
• PUT /users/123: Updates user 123 with the same data every time, so the result doesn’t change.

Non-idempotent example:

• POST /orders: Every time you call it, a new order is created, leading to different results.

What are the components of a HTTP request?

An HTTP request has four main parts:

1. Method: Tells the server what action to perform (e.g., GET, POST).
2. URL: Specifies the resource to act on (e.g., /users/123).
3. Headers: Contains metadata like content type or authorization tokens.
4. Body: Optional; used to send data (mainly in POST and PUT requests).

What are HTTP headers? Provide examples of commonly used headers in REST API.

HTTP headers are like little notes attached to your request or response, giving extra information.

Examples of common headers:

• Authorization: Includes credentials to authenticate.
  • Example: Authorization: Bearer <token>
• Content-Type: Specifies the format of the request body.
  • Example: Content-Type: application/json
• Accept: Tells the server what formats the client can handle.
  • Example: Accept: application/json
• Cache-Control: Sets caching rules.
  • Example: Cache-Control: no-cache

Design and Implementation of REST APIs in Java

How do you design a RESTful API? What are best practices?

Designing a RESTful API involves creating a system that’s simple, scalable, and easy to use. Here’s how you can do it:

1. Identify Resources: Think of everything you want to expose (like users, orders) as resources.
2. Use Proper URIs: Design URIs that are simple, consistent, and meaningful (e.g., /users/123).
3. Choose the Right HTTP Methods: Use methods like GET for fetching, POST for creating, PUT for updating, and DELETE for removing resources.
4. Send Meaningful Responses: Use appropriate HTTP status codes and include helpful error messages in the response.
5. Secure Your API: Use authentication methods like OAuth or API tokens. Always use HTTPS.
6. Enable Filtering and Pagination: Allow users to retrieve specific data by adding query parameters like /products?category=books&page=2.
7. Documentation: Provide clear documentation so developers can understand how to use your API.

Best Practices:

• Keep it stateless.
• Use versioning (/api/v1) to avoid breaking changes.
• Handle errors gracefully with detailed but simple messages.

What is the significance of URI in RESTful services?

A URI (Uniform Resource Identifier) is crucial in REST because it identifies the resources you’re working with. It acts like an address that lets the client know where to send requests.

Key points about URIs in REST:

• They should be simple and descriptive. For example, /users/123 is better than /getUserDetails?id=123.
• Use nouns, not verbs, to describe resources (/books/1, not /getBook).
• They’re hierarchical, making navigation intuitive (/users/123/orders/456).

How can you implement a RESTful API in Java? Provide a basic example.

In Java, you can use Spring Boot to create RESTful APIs easily.

@RestController  
@RequestMapping("/api/users")  
public class UserController {  

    @GetMapping("/{id}")  
    public User getUserById(@PathVariable Long id) {  
        return new User(id, "John Doe", "john.doe@example.com");  
    }  

    @PostMapping  
    public User createUser(@RequestBody User user) {  
        // Logic to save user  
        return user;  
    }  
}  

class User {  
    private Long id;  
    private String name;  
    private String email;  

    // Constructor, getters, and setters  
}  

Here, we created two endpoints: one for fetching a user by ID and another for creating a user.

What is the role of annotations like @RestController and @RequestMapping in Spring Boot?

@RestController: Combines @Controller and @ResponseBody, meaning every method in this class will return data (not a view). It’s perfect for building REST APIs.@RequestMapping: Maps a URL to a specific class or method. For example, @RequestMapping("/api/users") ensures all endpoints in the class start with /api/users.

How do you handle different HTTP methods in Spring Boot?

In Spring Boot, you use annotations like @GetMapping, @PostMapping, @PutMapping, and @DeleteMapping to handle various HTTP methods.

@RestController  
@RequestMapping("/api/products")  
public class ProductController {  

    @GetMapping  
    public List<Product> getAllProducts() {  
        return productService.getAllProducts();  
    }  

    @PostMapping  
    public Product createProduct(@RequestBody Product product) {  
        return productService.save(product);  
    }  

    @PutMapping("/{id}")  
    public Product updateProduct(@PathVariable Long id, @RequestBody Product product) {  
        return productService.update(id, product);  
    }  

    @DeleteMapping("/{id}")  
    public void deleteProduct(@PathVariable Long id) {  
        productService.delete(id);  
    }  
}  

What is @PathVariable and how is it used?

@PathVariable is used to extract values from the URI and pass them to the method.

@GetMapping("/users/{id}")  
public User getUser(@PathVariable Long id) {  
    return userService.findById(id);  
}  

Here, if the client sends a request to /users/123, the value 123 is mapped to the id parameter.

What is @RequestParam and how does it differ from @PathVariable?

@RequestParam extracts query parameters from the URL, while @PathVariable pulls values directly from the URI path.

Example of @RequestParam:

@GetMapping("/search")  
public List<User> searchUsers(@RequestParam String name) {  
    return userService.searchByName(name);  
}  
// URL: /search?name=John  

Difference:

• Use @PathVariable for mandatory path segments (/users/{id}).
• Use @RequestParam for optional or additional parameters (/search?name=John).

Explain the use of @ResponseEntity in REST APIs.

@ResponseEntity allows you to customize the response sent to the client, including the status code, headers, and body.

Example:

@GetMapping("/users/{id}")  
public ResponseEntity<User> getUser(@PathVariable Long id) {  
    User user = userService.findById(id);  
    if (user == null) {  
        return ResponseEntity.status(HttpStatus.NOT_FOUND).body(null);  
    }  
    return ResponseEntity.ok(user);  
}  

This makes it easy to handle both success and error cases elegantly.

How do you set custom HTTP status codes in a REST API?

You can set custom HTTP status codes using ResponseEntity or by annotating your methods with @ResponseStatus.

Using @ResponseStatus:

@ResponseStatus(HttpStatus.CREATED)  
@PostMapping("/users")  
public User createUser(@RequestBody User user) {  
    return userService.save(user);  
}  

Using ResponseEntity:

@PostMapping("/users")  
public ResponseEntity<User> createUser(@RequestBody User user) {  
    User savedUser = userService.save(user);  
    return ResponseEntity.status(HttpStatus.CREATED).body(savedUser);  
}  

What is the significance of @RequestBody and @ResponseBody annotations?

@RequestBody: Converts JSON from the request body into a Java object.
Example:

@PostMapping("/users")  
public User createUser(@RequestBody User user) {  
    return userService.save(user);  
}  

Here, the JSON { "name": "John", "email": "john@example.com" } is mapped to the User object.

@ResponseBody: Converts a Java object into JSON and sends it in the response.
Example:

@GetMapping("/users/{id}")  
public @ResponseBody User getUser(@PathVariable Long id) {  
    return userService.findById(id);  
}  

Together, these annotations ensure seamless conversion between JSON and Java objects in REST APIs.

Error Handling and Security

How do you handle errors in a REST API? Provide examples.

Handling errors effectively in a REST API ensures a better user experience and easier debugging. Here’s how you can do it:

1. Use Standard HTTP Status Codes: For example:
   • 400 for bad requests.
   • 404 for resources not found.
   • 500 for server errors.
2. Return Clear Error Messages: Include details like what went wrong and suggestions to fix it.

{
  "timestamp": "2024-12-11T12:34:56",
  "status": 404,
  "error": "Not Found",
  "message": "User with ID 123 not found",
  "path": "/api/users/123"
}

In Spring Boot:

@RestControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(ResourceNotFoundException.class)
    public ResponseEntity<Object> handleResourceNotFound(ResourceNotFoundException ex) {
        Map<String, Object> errorDetails = new HashMap<>();
        errorDetails.put("timestamp", LocalDateTime.now());
        errorDetails.put("status", HttpStatus.NOT_FOUND.value());
        errorDetails.put("error", "Not Found");
        errorDetails.put("message", ex.getMessage());
        errorDetails.put("path", "/api/users");
        return new ResponseEntity<>(errorDetails, HttpStatus.NOT_FOUND);
    }
}

What are the best practices for designing error responses in REST APIs?

• Be Consistent: Use a uniform structure for all error responses.
• Include Helpful Details: Provide timestamps, error codes, and suggestions.
• Avoid Overexposing: Don’t reveal sensitive server information in errors.
• Support Localization: Allow error messages in multiple languages if needed.

Example of a standard structure:

{
  "code": "USER_NOT_FOUND",
  "message": "User with ID 123 does not exist",
  "details": "Check the ID and try again",
  "timestamp": "2024-12-11T12:00:00Z"
}

How can you implement authentication in REST APIs?

There are various methods to implement authentication, such as:

1. Basic Authentication: Sends a username and password in the request header (Base64 encoded).
2. Token-Based Authentication: Issues a token after login (e.g., JWT).
3. OAuth2: A robust framework for securing APIs using access tokens.

Example with JWT in Spring Boot:

@PostMapping("/login")
public ResponseEntity<?> authenticateUser(@RequestBody LoginRequest loginRequest) {
    String token = jwtUtil.generateToken(loginRequest.getUsername());
    return ResponseEntity.ok(new JwtResponse(token));
}

What is the difference between Basic Authentication and OAuth2?

• Basic Authentication:
  • Simple, requires username and password in each request.
  • Less secure; credentials are often reused.
  • Ideal for small, internal applications.
• OAuth2:
  • Uses tokens for secure communication.
  • Allows granular permissions and third-party access without sharing credentials.
  • Suitable for large, scalable applications.

How do you secure REST APIs using Spring Security?

1. Add Dependencies: Include Spring Security and OAuth dependencies in your project.
2. Configure Security: Set up authentication and authorization rules.

Example:

@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.csrf().disable()
            .authorizeRequests()
            .antMatchers("/api/public/**").permitAll()
            .anyRequest().authenticated()
            .and()
            .httpBasic();  // or use JWT for token-based security
    }
}

What is CORS, and how do you handle it in REST APIs?

CORS (Cross-Origin Resource Sharing) controls which domains can access your API.

In Spring Boot:

@Configuration
public class CorsConfig {
    @Bean
    public WebMvcConfigurer corsConfigurer() {
        return new WebMvcConfigurer() {
            @Override
            public void addCorsMappings(CorsRegistry registry) {
                registry.addMapping("/api/**")
                        .allowedOrigins("http://example.com")
                        .allowedMethods("GET", "POST", "PUT", "DELETE");
            }
        };
    }
}

How can you prevent common vulnerabilities in REST APIs, like SQL injection and CSRF?

• SQL Injection:
  • Use parameterized queries or ORM frameworks like Hibernate.
  • Avoid dynamic SQL queries.
• CSRF (Cross-Site Request Forgery):
  • Enable CSRF protection in Spring Security.
  • Use anti-CSRF tokens in forms.
• General Best Practices:
  • Validate and sanitize inputs.
  • Use HTTPS.
  • Implement strong authentication and authorization.

What are the pros and cons of using API keys for REST API authentication?

Pros:

• Simple and easy to implement.
• Ideal for server-to-server communication.
• Provides limited access based on the API key.

Cons:

• API keys can be stolen if not secured properly.
• No built-in expiration or revocation.
• Not suitable for user-level permissions.

What is JWT (JSON Web Token), and how is it used in REST APIs?

JWT is a compact, self-contained token used for securely transmitting information between parties.

Structure:

• Header: Algorithm and token type.
• Payload: User and metadata.
• Signature: Verifies the token’s authenticity.

How it’s used:

1. Client logs in and receives a JWT.
2. Client sends the JWT in the Authorization header of every request.
3. Server verifies the token before processing the request.

Example Header:

Authorization: Bearer <JWT_TOKEN>

Explain the concept of rate limiting in REST APIs.

Rate limiting restricts the number of API requests a client can make within a specific time period.

Why it’s important:

• Protects against abuse or denial-of-service attacks.
• Ensures fair usage among clients.

Implementation Example in Spring Boot:
You can use libraries like Bucket4j or Redis to implement rate limiting.

@Component
@Aspect
public class RateLimiterAspect {
    private final Map<String, Integer> requestCounts = new ConcurrentHashMap<>();

    @Around("@annotation(RateLimit)")
    public Object rateLimit(ProceedingJoinPoint joinPoint) throws Throwable {
        String key = getClientKey();
        requestCounts.putIfAbsent(key, 0);

        if (requestCounts.get(key) > 100) {
            throw new RateLimitExceededException("Rate limit exceeded");
        }

        requestCounts.put(key, requestCounts.get(key) + 1);
        return joinPoint.proceed();
    }
}

Advanced REST API Concepts

What is HATEOAS, and how is it implemented in REST APIs?

HATEOAS stands for “Hypermedia as the Engine of Application State.” It’s a REST concept where an API response not only returns data but also includes links to related resources or actions. These links allow the client to navigate the API without needing extra documentation.

Example Implementation:
Imagine you retrieve a user’s data, and the response includes links to edit or delete that user:

{
  "id": 1,
  "name": "Alice",
  "links": [
    { "rel": "self", "href": "/users/1" },
    { "rel": "edit", "href": "/users/1/edit" },
    { "rel": "delete", "href": "/users/1/delete" }
  ]
}

In Spring Boot, you can use the HATEOAS library to add these links automatically.

Explain the concept of pagination in REST APIs. How do you implement it?

Pagination helps break large sets of data into smaller chunks, so clients can load them bit by bit, improving performance. Typically, pagination is controlled by parameters like page, size, and sort.

Example Response:

{
  "data": [
    { "id": 1, "name": "Item 1" },
    { "id": 2, "name": "Item 2" }
  ],
  "pagination": {
    "currentPage": 1,
    "totalPages": 5,
    "totalItems": 50
  }
}

In Spring Boot:

@GetMapping("/items")
public Page<Item> getItems(@RequestParam int page, @RequestParam int size) {
    Pageable pageable = PageRequest.of(page, size);
    return itemRepository.findAll(pageable);
}

What is versioning in REST APIs, and what are the different strategies for it?

Versioning in REST APIs is essential for managing updates without disrupting existing users.

Versioning Strategies:

• URI Versioning: /v1/users, /v2/users.
• Header Versioning: Custom headers like X-API-Version: 1.
• Query Parameter: /users?version=1.
• Content Negotiation: Specify versions in the Accept header, like application/vnd.api.v1+json.

Example in Spring Boot (URI Versioning):

@GetMapping("/v1/users")
public List<User> getUsersV1() { return userService.getUsersV1(); }

How can you cache REST API responses? Explain caching headers like ETag.

Caching improves performance by storing API responses temporarily.

Common Caching Headers:

• Cache-Control: Tells the client how long to cache a response (Cache-Control: max-age=3600).
• ETag: A unique identifier for the version of the data. It helps determine if the data has changed.

Example of ETag Usage:
If the client sends a request with If-None-Match, and the ETag matches, the server can respond with a 304 Not Modified instead of re-sending the data.

In Spring Boot:

@GetMapping("/users/{id}")
public ResponseEntity<User> getUser(@PathVariable Long id) {
    User user = userService.getUserById(id);
    return ResponseEntity.ok()
        .eTag(Integer.toString(user.hashCode()))
        .body(user);
}

What is the purpose of @ExceptionHandler in REST APIs?

@ExceptionHandler is used to handle specific exceptions thrown during request processing in Spring. It provides a clean way to manage errors and send appropriate responses.

Example:

@ExceptionHandler(UserNotFoundException.class)
public ResponseEntity<Object> handleUserNotFound(UserNotFoundException ex) {
    return ResponseEntity.status(HttpStatus.NOT_FOUND)
        .body(Map.of("error", ex.getMessage()));
}

How do you implement file upload/download in REST APIs?

For file uploads, use @RequestParam to handle multipart files.

File Upload Example:

@PostMapping("/upload")
public ResponseEntity<String> uploadFile(@RequestParam("file") MultipartFile file) throws IOException {
    String filePath = fileService.saveFile(file);
    return ResponseEntity.ok("File uploaded: " + filePath);
}

For file downloads, you can use ResponseEntity to return the file with proper headers.

File Download Example:

@GetMapping("/download/{fileName}")
public ResponseEntity<Resource> downloadFile(@PathVariable String fileName) throws IOException {
    Resource file = fileService.loadFile(fileName);
    return ResponseEntity.ok()
        .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + fileName + "\"")
        .body(file);
}

What are filters and interceptors in Spring, and how are they used in REST APIs?

• Filters are used for tasks like logging, authentication, and modifying requests or responses before/after they hit the controller.
• Interceptors are more for cross-cutting concerns (like logging or security), typically before the controller logic runs.

Filter Example:

@Component
public class LoggingFilter implements Filter {
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("Request received: " + request.getRemoteAddr());
        chain.doFilter(request, response);
    }
}

Interceptor Example:

@Component
public class AuthInterceptor implements HandlerInterceptor {
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        String token = request.getHeader("Authorization");
        return token != null && token.equals("valid-token");
    }
}

How do you implement asynchronous requests in REST APIs using Java?

Asynchronous requests allow the server to respond faster by not blocking resources while waiting for external operations to finish.

Example with CompletableFuture:

@GetMapping("/async")
public CompletableFuture<String> getAsyncData() {
    return CompletableFuture.supplyAsync(() -> "Async Data");
}

What is the difference between synchronous and asynchronous REST APIs?

Synchronous APIs: The client waits for the server to respond before continuing. This is the traditional approach.

Asynchronous APIs: The server responds immediately with a status, and the client handles the rest later. This can improve performance and responsiveness.

How can you test REST APIs in Java? Mention tools and approaches.

To test REST APIs in Java, you can use:

JUnit with MockMvc: A simple way to test controllers without starting a server.

@Test
public void testGetUser() throws Exception {
    mockMvc.perform(get("/users/1"))
        .andExpect(status().isOk())
        .andExpect(jsonPath("$.name").value("Alice"));
}

Postman: A manual testing tool to send requests and check responses.

REST Assured: A Java-based library for automated testing.

@Test
public void testGetUser() {
    given().when().get("/users/1").then().statusCode(200);
}

Integration and Deployment

What are the common tools for testing REST APIs? Explain Postman and Swagger.

Common tools for testing REST APIs include:

• Postman: A popular tool for manually testing REST APIs. It allows you to send HTTP requests (GET, POST, PUT, DELETE) to a server and view the responses. You can also automate tests and create collections of requests for reuse.
• Swagger/OpenAPI: Used for designing, documenting, and testing APIs. Swagger allows you to define the structure of your API using a standard format (OpenAPI Specification). It also provides an interactive UI where you can test the API endpoints directly from the documentation.

How do you document REST APIs effectively? What is the role of Swagger/OpenAPI?

Effective documentation helps users understand how to use your API. Swagger/OpenAPI makes this easier by automatically generating interactive and detailed documentation.

• Swagger creates a clear and interactive documentation for your API where users can test endpoints and see the responses directly in their browser.
• OpenAPI Specification defines the structure of the API, including available endpoints, request formats, response formats, authentication, and error handling.

Using Swagger UI with OpenAPI allows developers to interact with the API in real-time, making it more understandable.

What is the role of REST APIs in microservices architecture?

In microservices architecture, REST APIs serve as the communication bridge between services. Each microservice is responsible for a specific task, and REST APIs allow them to interact with each other, exchange data, and trigger actions. REST APIs ensure that services can remain independent but still collaborate seamlessly.

How do you integrate REST APIs with a database in Java?

To integrate a REST API with a database in Java:

1. Set up a database: Choose a database like MySQL, PostgreSQL, or MongoDB.
2. Use JPA (Java Persistence API): You can use JPA with Hibernate to map your Java objects to database tables.
3. Create an entity class: Define your data model (entity) and annotate it with @Entity, @Table, etc.
4. Create a repository: Use Spring Data JPA’s repository interfaces like JpaRepository to interact with the database.
5. Expose API endpoints: In your controller, use @GetMapping, @PostMapping, etc., to expose endpoints that interact with the database.

Example:

@Entity
public class User {
    @Id
    private Long id;
    private String name;
}

@Repository
public interface UserRepository extends JpaRepository<User, Long> {}

What is a REST client, and how can you build one using RestTemplate in Spring Boot?

A REST client is a tool or code used to send requests to and receive responses from REST APIs. In Spring Boot, you can build a REST client using RestTemplate.

Example of using RestTemplate to make a GET request:

import org.springframework.web.client.RestTemplate;

@RestController
public class UserController {
    private RestTemplate restTemplate = new RestTemplate();
    
    @GetMapping("/getUser")
    public User getUser() {
        String url = "https://api.example.com/users/1";
        return restTemplate.getForObject(url, User.class);
    }
}

What is the purpose of WebClient in Spring WebFlux? How does it differ from RestTemplate?

WebClient is the non-blocking, reactive alternative to RestTemplate. It is part of Spring WebFlux and is used for making asynchronous HTTP requests. Unlike RestTemplate, which is blocking and synchronous, WebClient allows for non-blocking operations, which is useful in high-concurrency applications.

Key differences:

• RestTemplate: Synchronous (blocking).
• WebClient: Asynchronous (non-blocking), part of Spring WebFlux for reactive programming.

What are the differences between REST and GraphQL?

REST:

• Focuses on resources and uses fixed endpoints for each type of data.
• Returns the same set of data for a request, even if not all data is needed.

GraphQL:

• Allows clients to request only the data they need, reducing over-fetching or under-fetching.
• Uses a single endpoint to handle all types of requests, unlike REST which has multiple endpoints.

Example:
In REST, to get a user and their posts, you may need to make two requests (/users and /posts). In GraphQL, you can get both in one query.

How do you deploy RESTful services in Java? Provide steps for deploying a Spring Boot application.

To deploy a Spring Boot application with RESTful services:

1. Build the project: Use mvn clean package or gradle build to create a .jar or .war file.
2. Deploy the application: You can run the .jar file directly using java -jar myapp.jar, or deploy it to a server like Tomcat if it’s packaged as .war.
3. Host on a cloud: You can deploy the application on cloud platforms like AWS, Azure, or Google Cloud.
4. Configure database and environment: Set up the database connections and environment variables.

What is the importance of monitoring REST APIs in production?

Monitoring REST APIs in production is crucial for ensuring performance, identifying issues, and maintaining a good user experience. By tracking metrics like response times, error rates, and throughput, you can proactively fix problems before they affect users.

Tools: Prometheus, Grafana, and New Relic can help monitor API health and performance in production.

How do you improve the performance of REST APIs in Java? Provide practical tips.

To improve the performance of REST APIs in Java:

1. Optimize database queries: Use indexing, limit joins, and avoid N+1 queries.
2. Use caching: Cache frequent requests using tools like Redis to reduce database load.
3. Asynchronous processing: Use asynchronous calls for non-blocking operations, which improves scalability.
4. Use efficient data formats: Prefer lightweight formats like JSON over XML for smaller payloads.
5. Load balancing: Distribute traffic across multiple servers to avoid bottlenecks.

Read More : Top 50 Spring Boot Interview Question

Read More : Top 50 Microservices Interview Question