- Tell me about your experience and skills

Entry-Level: Highlight your academic projects, internships, and exposure to tools/technologies like Java, Spring Boot, Hibernate, REST APIs, and front-end frameworks like Angular/React. Focus on what you’ve learned and implemented. "I worked on a project to develop a library management system using Spring Boot and Angular. My role involved building REST APIs for book management and user authentication." Experienced: Talk about your hands-on experience with end-to-end development, deployments, and architectural design. Mention team management or problem-solving in live production.

"I have 5 years of experience in developing scalable microservices using Spring Boot and managing deployment pipelines with Jenkins and Docker."

- Monolithic Vs Microservices

Monolithic

- Single, large application where all modules are tightly coupled.
- Hard to scale and maintain.
- Example: A legacy e-commerce system where all functionalities (user management, orders, payments) are in a single codebase.

Microservices

- Independent services handling specific functionalities.
- Easier to scale, deploy, and maintain.
- Example: Amazon’s system, where user management, payment, and recommendations are independent microservices.
- What are the challenges you have seen in Microservices?

Common Challenges

- Communication Issues: Services need proper mechanisms (e.g., REST, gRPC) for interaction.
- Data Consistency: Managing distributed transactions (use of tools like Saga).
- Deployment Complexity: Managing multiple services using orchestration tools (e.g., Kubernetes).
- Debugging: Difficult to trace errors across services.
- How many Microservices have you developed?

Mention specific services and their functionalities. "I developed 5 microservices for an e-commerce platform, handling user authentication, order management, inventory, payment, and notifications."

- How do you make a call from one service to another?

There Are Two Common Methods

- REST API: Use HTTP-based communication.




- Service Discovery: Use tools like Eureka or Consul for service lookup.

// Example using RestTemplate in Java RestTemplate restTemplate = new RestTemplate(); String response = restTemplate.getForObject("http://service-b/api/data", String.class);

- How do you specify the hostname in REST URL?

Use workplace variables or configuration files . // Example in Spring Boot service.url=http://localhost:8080

- What is Heartbeat?

A mechanism to check if a service is alive. Example: Using Spring Actuator, a service can expose /actuator/health, which other services can ping to check the status.

- How will you know the other service is up and running?

Use health-check endpoints or monitoring tools like Prometheus and Grafana . // Example using RestTemplate RestTemplate restTemplate = new RestTemplate(); String status = restTemplate.getForObject("http://service-b/actuator/health", String.class);

- What is Service Discovery?

Automatically detects and registers services, avoiding hardcoding URLs. Example: Netflix Eureka or Consul dynamically manage service registration.

- What is Eureka Server?

A service registry by Netflix for service discovery. Example: Service A can find Service B by querying Eureka Server.

- Monitoring of Microservices: Which tools are you familiar with?

Entry-Level: Learn tools like Spring Boot Actuator, Postman, and basic logging.

Experienced

- Prometheus + Grafana: For metrics and visualization.
- ELK Stack (Elasticsearch, Logstash, Kibana): For centralized logging.
- Zipkin/Jaeger: For distributed tracing.

Example Workflow: Use Prometheus to collect metrics and visualize them in Grafana dashboards.



Set up alerts for critical thresholds.

- Explain the Architecture of the Microservices.

Components

- API Gateway: Routes requests to services (e.g., Zuul, Spring Cloud Gateway).
- Service Discovery: Registers and discovers services (e.g., Eureka).
- Database: Each service has its database for separation of concerns.
- Load Balancer: Ensures traffic distribution.
- Monitoring: Tracks service health and performance.
- How is the request routed to Microservices?

Via API Gateway , which routes based on the URI. Example: A user’s login request is routed to http://api-gateway/login.

- Where is security validation handled?

Use API Gateway or Authentication Service . Example: JWT token validation in Spring Boot:

@RequestMapping("/validate") public boolean validateToken(String token) { return jwtService.validateToken(token); }

- What is Route Filtering?

Filters modify requests/responses in an API Gateway. Example: Zuul filters for logging or adding headers.

- Where does the control start in a Spring Boot application?

It Starts In The Main() Method public static void main(String[] args) { SpringApplication.run(Application.class, args); }

- What are the basic elements needed to start the Spring Boot application?
- @SpringBootApplication
- application.properties
- REST Controller for endpoints.
- What are the main features of Spring Boot?
- Auto-configuration
- Embedded servers (e.g., Tomcat)
- Actuator for monitoring
- Dependency management with Spring Boot Starter.
- Which version of Java have you worked on?

Highlight your expertise. "I have worked on Java 8, 11, and 17, focusing on features like Streams and Records." List names = Arrays.asList("Alice", "Bob"); names.forEach(System.out::println);

- What are the main features of Java 8?
- Lambda Expressions: Simplify functional programming.
- Streams API: For bulk operations on data.
- Default Methods: In interfaces.
- Optional Class: Avoid NullPointerException.

📌 Top Java Interview Questions & Answers for 0-5 Years Experience | Part 1 (Bengaluru)
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