Java Microservices Interview Questions for Freshers

1. What are Microservices?

Microservices is an architecture in which the application performs as a loosely coupled service that can be developed, deployed, and maintained independently. Each service in this architecture is called a Microservice.

• In Microservices, each service performs a different and unique function.
• Through APIs it communicates with other services by focusing on the business strategies.
• Different microservices can be used for different architecture and languages.

2. When and Why to use Microservices?

For large or complex projects microservices are the best choice for scalability, flexibility, and faster development with evolving requirements. Microservices are useful when the application or our project needs to be more scalable and manageable or requires more resources.

• Microservices are ideal when the monolithic applications need to be optimized and modernized.
• Each service can be independently developed, deployed, and maintained.
• To reduce time, for scalability, fast development, low cost, and cloud-native development microservices are ideal.
• We should not use microservices for simple applications which can be managed by monolithic architecture.

3. Explain the workings of Java Microservices Architecture.

In Java Microservices architecture, an application is divided into small processes or we can call them sub-processes. Each process runs on its functionality. All the sub-processes communicate with each other through small protocols. It manages better scalability and coordination between services.

Below is the Architectural diagram of Java Microservices:

4. What are the Pros and Cons of Java Microservices?

There are so many benefits and drawbacks in Java Microservices architecture.

Pros:

• We can use different technologies using microservices.
• It takes care of the security of each service.
• More than one service can be parallelly developed and deployed.
• Services are independently managed.
• Better scalability and agility.

Cons:

• Communication between microservices can be complex.
• Large numbers of service management is difficult.
• Handling microservices with different business requirements is a tough task.
• So many configurations have to do which increases efforts.
• Network maintenance is difficult.
• Complex development and Security issues.

5. What are the main features of Java Microservices?

There are so many features of Java Microservices. Some of the main features are listed below:

• Deployment: It breaks an application into small services, because of this it is possible to deploy and develop each of these services independently.
• Decentralization: Data storage management is decentralized. Each of the services has its own data related to a particular business functionality.
• Loosely Coupled: If a single process fails, it will not affect the other services and the entire system.
• Security: It provides authentication and authorization based on the Role-based access model (RBAC).
• Scalable: Based on the requirements, services can be scaled which results in better scalability.

6. What is Monolithic architecture?

A monolithic architecture-based application is built as a single unit means inside a single code base, all the functionality and modules of the application are available.

• Before microservices, all modules were there in a single project.
• It supports tightly coupled architecture.

• Here, we have a server. The server can be Tomcat, jetty, or any type.
• In this server, we have deployed our application.
• Inside this web application, we need to deploy all the modules of an application.
• The outcome will be a WAR file. Only if we deploy the war file, these modules will be available.

This is the Monolithic Architecture.

7. Explain SOA.

SOA refers to Service-Oriented Architecture.

• This SOA architecture is a collection of multiple services.
• These multiple services do communicate with each other by using some standardized protocols.
• Also in this design approach, applications are build as a collection of services that are loosely coupled.

It communicates with each service over a network and then implements a specific business function. The communication could be the normal passing of data or more than two services sharing some common activity or any type of coordination.

8. What is the difference between Monolithic, SOA, and Microservices Architecture?

Below are the basic differences between the Monolithic, SOA, and Microservices Architecture.

9. Explain the design patterns of Java Spring Boot Microservices.

• Service Registry and Discovery: Services automatically register in a central registry, allowing others to identify and interact with them dynamically.
• API Gateway: It acts as a customer entry point and forwards requests to appropriate microservices to provide additional functionality such as authentication and rate limits.
• Circuit Breaker: It monitors the availability of services and protects from failures by sending requests or by providing responses if service is unavailable.
• CQRS (Command Query Responsibility Segregation): It separates the read and write operations. Also, it optimizes each and every operation separately for efficiency.
• Saga Pattern: It manages distributed tasks by organizing a sequence of local transactions.
• Database per service: Each of the services has separate databases. This ensures data isolation and also enables scaling and individual development.
• Asynchronous messaging: Each services communicate with each other through message queues like Kafka or RabbitMQ.

10. What are the Main Components of Java Spring Boot Microservices?

The main components of Java Spring Boot Microservices include:

• Services
• Service Registry
• API Gateway
• Cloud Infrastructure
• Containerization and Orchestration
• Message Broker
• Security
• Monitoring

11. Name three commonly used tools for Java Spring Boot Microservices.

There are different tools used for Java Spring Boot Microservices, some important tools are,

1. Docker: This is a containerization tool that allows developers to put applications and their dependencies in a lightweight container, and provide stability across multiple environments.
2. Kubernetes: This is an open-source container orchestration tool and it automates the scaling, deployment, and management of containerized applications. It offers features like service discovery, load balancing etc.
3. Spring Cloud: This is a framework in the Spring ecosystem for building microservice-based applications. It is used to develop cloud-native applications. It offers features like service discovery, configuration management, circuit breakers etc.

12. How do Microservices Communicate with each other?

In Microservices, multiple services run independently. Services communicate with each other through,

• HTTP/REST: These are light-weight protocols used for perform communication between two services.
• Message queues: Message queues such as Kafka or RabbitMQ used to make connection.
• RPC (Remote Procedure Call) Framework: RPC frameworks such as gRPC uses in services for communication purposes.

These methods of communication enable loosely coupled interaction, scalability, and flexibility in distributed systems.

For more details please refer to this article: How do Microservices Communicate With Each Other?

13. How to Process the Request and Response between Two Services?

By establishing communication between the two services, microservices can handle requests and responses between any two services using XML (Extensible Mark-up Language) and JSON (JavaScript Object Notation).

• XML and JSON are data exchange formats and it helps to generate requests and responses between two services.
• Most important thing is the data exchange format and both the services have to know the data exchange format to request and respond accordingly.
• If we compare both formats, JSON is very simple to use in Microservices.

Microservices, also called Microservices Architecture, is a software development approach that involves building large applications as a collection of small functional modules. This architectural approach is widely adopted due to its ease of maintenance and faster development process.

Microservices with the Spring Boot framework break down complex applications into smaller services, loosely coupled services, each focusing on a specific business capability. This architecture promotes agility, scalability, and resilience, leveraging technologies like Docker, Kubernetes, and RESTful APIs for seamless communication and deployment in distributed environments.

Here, in this Java Microservices Interview Questions we have gathered a list of the Top 30 Java Microservices Interview Questions with Answers that are commonly asked in recent interviews. Whether you are a fresher or an experienced professional with 2, 5, 8, or 10 years of experience, going through these microservices interview questions will help you prepare for your upcoming technical interviews and increase your chances of succeeding.