Spring Cloud Interview Questions

The popularity of the Spring Cloud framework has grown over the years. It continues to thrive in the web framework market with the cutting-edge benefits it offers to developers. Becoming a Spring Cloud Certified Professional can help you to bag top-paying jobs related to Java.

In this article, MindMajix’s experts have shortlisted a definitive list of the top 30 Spring Cloud Interview Questions and Answers to help you land a top-notch job in the field.

We have covered various Spring Cloud-related Interview Questions, ranging from basic to advanced.

• Freshers
• Experienced

Top 10 Spring Cloud Frequently Asked Questions

1. Spring Cloud vs Spring Boot.
2. What are the key Features of Spring Cloud?
3. What are the components of Spring Cloud?
4. What is Spring Cloud Bus?
5. Explain load balancing in Spring Cloud.
6. What is Spring Cloud Gateway?
7. What is eureka in Spring Cloud?
8. Is Spring Cloud the same as AWS?
9. What is Spring Cloud Stream?
10. Describe Spring Cloud Azure

Spring Cloud Interview Questions For Freshers

1. What are Microservices?

Microservices are a modern approach to software development, where you can deliver the application code in small, manageable pieces, independent of others.

Building ready-to-use apps add more flexibility and resilience to the code. 

Spring Boot's many purpose-built features make it easier to construct and operate microservices at scale. Also, microservices architecture is incomplete without Spring Cloud, which facilitates administration and enhances fault tolerance.

If you want to enrich your career and become a professional in Spring Cloud, then enroll in "Spring Cloud Training" - This course will help you to achieve excellence in this domain.

2. Spring Cloud vs Spring Boot.

Spring Cloud and Spring Boot are part of the Spring framework and serve different requirements in Microservices.

The below table illustrates the key differences between Spring Cloud and Spring Boot

Spring Cloud	Spring Boot
Spring Cloud is a configuration server technology that interacts with many services and collects into one application.	Spring Boot is a Java-based framework that works on the auto-configuration of Web applications.
It’s a part of Spring Boot.	It’s a standalone, app-centric application framework.
Spring Cloud works for microservices to manage configuration.	Spring Boot works for creating microservices.
Spring Cloud requires numerous dependencies.	Spring Boot applies less dependency.

3. What is Spring Cloud and mention the need for it?

Spring Cloud is a set of ready-to-use components used in building distributed applications at the enterprise level. It's widely employed as a framework to avoid difficulties observed in distributed environments like load balancing, intelligent routing, circuit breaking, service discovery, cluster state, and many more.

Related Article: Spring Cloud Tutorial

4. What are the key Features of Spring Cloud?

Spring Cloud provides out-of-box experiences to typical use cases and extensibility mechanisms. A few essential features of Spring Cloud are listed below

• Intelligent routing and service discovery

When building microservices on Spring Cloud, there is a special connection to the first two essential microservices: configuration service and discovery service.

The above diagram shows the grouping of four microservices. The connection between each service exhibits dependency. Each service is dependent upon the other. The configuration services lie at the top, while the discovery services are at the bottom.

• Distributed / versioning configuration

Each instance of microservice configuration gets done through distributed configuration. The "Spring Cloud config server" offers client-side assistance for distributed systems' externalized configuration. It serves as a central place to control the external attributes of apps across multiple environments.

• Load balancing

It efficiently distributes network traffic among several backend servers or a server pool. The load balancing objective includes maximizing throughput, decreasing response times, increasing efficiency, and optimizing resource consumption. It avoids resource exhaustion on any one source. You can improve reliability and availability by implementing redundancy, multiple components, and load balancing.

• Distributed Messaging

The features of the distributed messaging system include dependability, scalability, and persistence. The messaging pattern follows the publish-subscribe (Pub-Sub) model. The publisher and subscribers in the Pub-Sub paradigm are the parties who send and receive messages, respectively. The two most widely used high throughput messaging systems are Apache Kafka and RabbitMQ.

• Global locks

These prevent multiple threads from accessing the same resource simultaneously. To avoid such a scenario, the programmer uses a lock mechanism. After using the resources, each thread releases the lock so the following thread can utilize them.

• Service-to-service calls

This feature demonstrates "how a microservice interacts with other dependent services through service registry or Eureka server." It follows a specific order:

1. Registering the service
2. Fetching the Registry
3. Finding the downstream service
4. Resolving the Underlying IP address
5. Call the rest Endpoint

• Circuit Breaker

Microservice calls are stopped by circuit breakers when they are aware that a request may fail or time out. By doing this, clients can avoid wasting valuable resources on responding to requests most likely to fail.

• Cluster state

An application can participate in leadership elections and cluster state by working with other apps to organize a cluster leadership using a third-party technology like Kubernetes.

5. What are the components of Spring Cloud?

Spring Cloud components are easy to plug and play tools that let users build common use patterns for a distributed system. Below listed are the core components of Spring Cloud:

• Configuration

Spring Cloud Configuration supports server-side and client-side external configuration in a distributed system. Using a config server across all environments, you can manage external properties for applications. 

• Service Discovery

This feature allows the detection of services and devices over the network automatically. There are two service discovery patterns: server-side discovery and client-side discovery.

1. In client-side discovery, the client is responsible for locating the services in the network. The customer requests by selecting one of the available services and using a load-balancing method.
2. In the server-side discovery, the client uses a load balancer to send an HTTP request to a service. Each request is routed to an accessible service instance by the load balancer once it contacts the service registry. Like client-side discovery, service instances are added to and removed from the service registry.

• Circuit Breakers

Circuit breakers determine when to open and close the circuit and what to do in the case of a failure. The circuit breaker smoothly manages all service failures when they occur. The three states of the circuit breakers are OPEN, CLOSED, and HALF-OPEN.

• Routing and Messaging

Since the cloud application comprises several microservices, connectivity will be essential. While Open Feign and Netflix Ribbon support routing, RabbitMQ or Kafka support communication. In Spring Cloud, both HTTP requests and messages support communication.

• API Gateway

With API Gateway, we may route requests to link services, either internal or external. 

• Tracing

A tracing is a single data request made to the application.

• CI Pipeline and Testing

The Spring Cloud pipelines are opinionated (self-important) pipelines generated automatically using Jenkins and Concourse for the application. The development, testing, and deployment of a cloud-native application across various services are essential to its success.

6. What is Spring Cloud used for?

Spring Cloud helps you to take full advantage of creating microservices in the cloud. It allows developers to cloud-native apps using service discovery, client-side load balancing, distributed configuration, routing, and fault tolerance.

7. What is Spring Cloud Bus?

Spring Cloud Cloud helps you to connect the distributed system nodes with a lightweight message broker. It helps broadcast state changes or management rules (e.g., configuration modifications). Majorly helps in refreshing configurations across multiple instances. Kafka and AMQP broker implementations support Spring Cloud Bus. 

8. What is Spring Cloud Config?

Ans. In distributed systems, the Spring Cloud Config is a client/server approach to store and manage external configurations across numerous apps and environments. 

It consists mainly of two components: Config Server and Config Client. Config Server manages external properties of apps across all environments.

The configuration store is ideally versioned under the Git version control and changed at the application's run time.

9. Explain load balancing in Spring Cloud.

Load balancing plays an efficient role in building modern fault-tolerant systems. In distributed systems, the services must communicate with each other either synchronously or asynchronously. 

When a service connects synchronously, it's easy for those to load balance the request. There are two ways to do this: 

• Server-side Load Balancing: The workers are fronted by a piece of software that divides up the incoming requests among them.
• Client-side Load Balancing: The requests are distributed among the workers by the caller server. The advantage of client-side load balancing is that it eliminates the need for a load balancer as a separate component. Netflix Ribbon and Spring Cloud Load Balancer are the popular client-side load balancer to manage that situation.

10. List a few Spring Cloud Annotations.

Spring Cloud uses various annotations to provide functionality instead of implementing a specific interface from the framework. Now, let's see a few of the Spring Cloud annotations that you need to know:

Annotation	Description
@EnableConfigServer	This annotation is a very useful annotation that turns your app into a server so that other apps can use the configuration.
@EnableEurekaServer	This annotation makes your app a Eureka discovery service, such that the other apps can locate services through it.
@EnableDiscoveryClient	This annotation registers your app in the service discovery and finds other services.@EnableCircuitBreaker
@EnableCircuitBreaker	This annotation configures Hystrix circuit breaker protocols.
@HystrixCommand(fallbackMethod = “fallbackMethodName”)	This annotation usually marks methods to fall back to another way if they can't succeed.

11. Explain Spring Cloud dependency with an example.

Spring Cloud has multiple packages named dependencies that help in building cloud applications. 

In the following example, we will see the internal working of different configurations to make this work. We will use the use case of the restaurant:

• Restaurant Service Discovery − Registers the service address.
• Restaurant Customer Service − Delivers the Customer information to the client and other services.
• Restaurant Service − Gives Restaurant information to the client. Uses Customer service to obtain the customer's city information.
• Restaurant Gateway − Serves as an entry point for the application. 

12. What is Spring Cloud Gateway?

Spring Cloud Gateway is a library to build API gateways on top of the Spring ecosystem. It allows a simple and effective way of routing API requests and cross-cutting concerns such as security, metrics, and resiliency.

There are three essential parts that make up Spring Cloud gateway. They are - 

• Route −These are the fundamental blocks of the gateway which contain the URL to which the request is to be forwarded. And the filters and predicates applied to the incoming requests.
• Predicate − These are the conditions that must be satisfied to redirect incoming requests to internal microservices. 
• Filters − These serve as the places where you can modify requests before being sent to internal microservices or returned to the client.

13. What is the use of Hystrix in Spring Cloud?

Hystrix is a library that helps in controlling service interactions through fault tolerance and latency tolerance. It isolates the points of access between the services, stops the cascading failures, provides fallback options, and improves the system's overall resilience.

For example, whenever you call a third-party application, it takes extra time to send the response. At that time, control goes to the fallback method and brings the custom response to your application.

14. Describe Service discovery.

Service discovery plays the most critical part when an application gets deployed as microservices in the cloud. It helps track the service address and the ports through which you can contact service instances. The three essential components of service discovery are:

• Service Instances − Handles incoming requests and responds to service.
• Service Registry − Tracks the service instance addresses. The service registry requires the service instances to register their addresses.
• Service Client − To find out the addresses of instances, the service client calls the service registry.

15. What is eureka in Spring Cloud?

Eureka is a service discovery tool that allows the registration and discovery of services. It employs a client-server architecture, with the server holding all the data about a registry of all the services.

When a client requires a service discovery, it interacts with the server and calls a list of all the services that have been registered. And then, the server responds with all the service lists matching the client's request.

Spring Cloud Interview Questions For Experienced

16. What best practices must you follow while developing Spring Cloud Applications?

Here are a few critical best practices you must follow while developing Spring Cloud applications:

• First, always use the latest versions of Spring Cloud and Spring Boot.
• Configure the Eureka server to use SSL for connectivity.
• Utilize load balancer for traffic distribution 
• Monitor the Eureka server for any issues that may arise.

17. How can you verify that the application registers with the proper instance of the Eureka Server?

By configuring the application to register with a particular instance of Eureka Server by configuring the eureka.instance.hostname property to the hostname or IP address of the Eureka Server instance that you wish to register with.

18. What protocols does Eureka follow?

Eureka follows two different protocols: the native Java protocol and the Apache Thrift protocol. 

1. The native java protocol is easy to use and most preferred among users.
2. The Apache Thrift protocol is more effective but needs extra configuration.

19. What are the advantages of using Eureka over Consul or Zookeeper?

Eureka has numerous advantages compared to other service registries.

1. It's easy to set up.
2. It has in-built fault tolerance, meaning that if any instance goes down, others continue to function.
3. Highly scalable 

20. How many instances of Eureka should you run in production?

Recommended to run at least three instances of Eureka in production. This helps high availability and failover even if one server goes down.

21. Is Spring Cloud the same as AWS?

No. Spring Cloud is a group of tools operated in the cloud, whereas AWS is one of the cloud choices for application deployment.

22. What is Spring Cloud AWS?

Spring Cloud AWS (Spring Cloud for AWS) is a part of the Spring Cloud project that provides various tools (software) for integrating multiple Amazon Web Services hosted services.

23. What are the key modules that Spring Cloud AWS offers?

Ans. Spring Cloud AWS provides the following modules.

• Spring Cloud AWS Core
• Spring Cloud AWS JDBC
• Spring Cloud AWS Context
• Spring Cloud AWS Messaging
• Spring Cloud AWS Secrets Manager Configuration
• Spring Cloud AWS Parameter Store Configuration

24. Describe Spring Boot CLI.

The main objective of Spring Boot CLI is to deliver command-line features for Spring Cloud. Through that, we can write groovy scripts to execute Spring Cloud component applications. 

25. Can you brief me about Spring Cloud Commons?

Spring Cloud Commons provides features as two libraries: Spring Cloud Context and Spring Cloud Commons.

• Spring Cloud Context offers unique services and utilities for Spring Cloud application context.
• Spring Cloud Commons is a group of standard classes and abstractions used in various Spring Cloud implementations.

26. What is Spring Cloud Stream?

Spring Cloud Stream is a framework for developing highly scalable event-driven microservices connected to shared messaging systems.

The core parts of Spring Cloud Stream are as follows:

• Destination Binders: Responsible for external messaging systems integration.
• Destination Bindings: Acts as a gateway between the application code and external messaging systems.
• Message: The canonical data structure used to interact with Destination Binders. 

27. What is the use of Spring Cloud Zookeeper?

The main objective of Spring Cloud Zookeeper is to support the Apache Zookeeper integrations through autoconfiguring and binding to the Spring Environment.

You can configure the common patterns inside the app using simple annotations and develop large distributed systems with Zookeeper.

28. Describe Spring Cloud Azure

Spring Cloud Azure is an open-source project that simplifies integrating Spring with Azure services. With just a few lines of configuration code and minor code changes, it provides developers with a Spring-idiomatic way to connect to and use Azure services. 

29. Explain Spring Cloud Netflix.

Spring Cloud Netflix supports Netflix OSS integrations that autoconfigure and bind to the Spring environment. You may easily activate and configure the common patterns inside your application with a few simple annotations, create large distributed systems, and use Netflix components.

30. Mention a few commonly used Spring Cloud modules in Microservices projects?

Here are the commonly used Spring Cloud modules in Microservices projects

• Spring Cloud Config
• Spring Cloud Circuit Breaker
• Spring Cloud Gateway
• Spring Cloud Stream
• Spring Cloud Sleuth
• Spring Cloud Bus
• Spring Cloud OpenFeign
• Spring Cloud Security

Most Commonly Asked Spring Cloud FAQs

1. Is Spring Cloud a Cloud platform?

Spring Cloud is an open-source library that makes creating JVM applications simple for the cloud. It allows applications to connect to services and quickly find more information about the cloud environment across many clouds.

2. What is the difference between Spring Cloud and AWS?

The significant difference is AWS is one of the popular cloud solutions for app deployment, whereas Spring Cloud is a set of programs often used in the cloud.

3. What is the difference between Spring Cloud and Kubernetes?

The critical difference is Spring Cloud handles every microservice architecture challenge inside the JVM. At the same time, Kubernetes tries to make the problem disappear for the developers by resolving it at the platform level. 

4. What problems are solved by Spring Cloud?

Spring Cloud can solve the following

• Network issues, bandwidth challenges, latency overhead, security issues, and other issues with distributed systems
• Redundancy issues occur in distributed systems.
• Load balancing between resources.
• Performance issues.
• Service discovery challenges inside a cluster for smoother communication.

5. What is Spring Cloud routing?

The Spring Cloud Gateway processes requests to downstream services using routing.

6. What is a Spring Cloud Load Balancer?

The Spring Cloud Load Balancer helps us to create apps that interact with other applications in a load-balanced manner. 

7. Is Spring Boot and Spring Cloud the same?

Spring Boot helps to build independent Microservice applications, while the Spring Cloud helps us to set up communication between those services.

8. What is ZUUL in the Spring Cloud?

Applications built with Spring Boot and using a microservices architecture are routed through the Zuul server. Zuul routes requests to particular microservices dynamically.

9. What are the advantages of Spring Cloud?

The main advantages of Spring Cloud

• Quick development Time: Using Spring Cloud, developers can quickly deliver projects while maintaining code quality.
• Easy to use: Spring Cloud can easily integrate existing Spring projects.
• Developers focus on business logic: Spring Cloud supports all the boilerplate code to execute the cloud's common design patterns. Thus developers can focus on business logic without the need to build and manage this boilerplate code.

Tips to clear Spring Cloud Interview

Here are a few tips to follow to get through this with flying colors

• Do a background search

You must do a background search of the company before you head to the interview. This helps to understand the types of questions that a particular interviewer might ask.

• Give some real-time examples

Try to use some real-world examples while responding to the questions. This demonstrates you have an in-depth understanding of the subject.

• Talk about your multi-skills

Talk about the other valuable information or skills you have in addition to Spring Cloud that you have obtained in the past. This ensures that you are the best fit for the job and sets you apart.

• Domain expertise

Review the job description. If there are any tools or skills you haven't used earlier, get familiar with them before attending the interview. 

• Finally, be confident!

No matter how much you practice, you won't feel confident on the big day! This can result in losing the dream job you are waiting for.

Conclusion

Now that you are familiar with the top Spring Cloud interview questions.  And in case you are looking for ways to enhance your web development skill set? Then we recommend you check out our Spring Cloud Certification Training Course to gain the skills needed in the workplace.

If you have any questions for us? Feel free to share them in the comments area. Soon, our team of experts will review and respond to them.