Spring Cloud Interview Questions and Answers

In this article, we will discuss a few important Spring Cloud interview questions with answers.

1. What is Spring Cloud?

Spring Cloud provides tools for developers to quickly build some of the common patterns in distributed systems or Microservices projects.

For example, common patterns such as configuration management, service discovery, circuit breakers, intelligent routing, micro-proxy, control bus, one-time tokens, global locks, leadership election, distributed sessions, and cluster state.

Spring Cloud provides various tools or modules for developers to build common design patterns to solve different infrastructural concerns in Microservices projects and focus on their main business problems.

Watch my YouTube video to understand Spring Cloud:

2. Explain Spring Cloud Features?

Spring Cloud offers below features:
  • Distributed/versioned configuration 
  • Service registration and discovery 
  • Routing 
  • Service-to-service calls 
  • Load balancing 
  • Circuit Breakers 
  • Distributed messaging
  • API Gateway
  • Distributed tracing

3. Explain Service Registry and Discovery

In microservices projects, Service Registry and Discovery play an important role because we most likely run multiple instances of services and we need a mechanism to call other services without hardcoding their hostnames or port numbers. 

In addition to that, in Cloud environments service instances may come up and go down anytime. So we need some automatic service registration and discovery mechanism. 

Spring Cloud addresses this problem by providing Spring Cloud Netflix Eureka project to create a Service Registry and Discovery.

Check out a complete example: Spring Cloud Netflix Eureka Example

4. Explain API Gateway

API Gateway provides a unified interface for a set of microservices so that clients do not need to know about all the details of microservices internals. 

API Gateway centralizes cross-cutting concerns like security, monitoring, rate limiting, etc.

Spring Cloud provides Spring Cloud Gateway to create API Gateway

Check out the complete example: Spring Boot Microservices - Spring Cloud API Gateway

Watch my YouTube video to understand how API Gateway works:

5. How to Implement API Gateway using Spring Cloud?

Spring Cloud provides a Spring Cloud Gateway library for building an API Gateway on top of Spring WebFlux. Spring Cloud Gateway aims to provide a simple, yet effective way to route to APIs and provide cross-cutting concerns to them such as security, monitoring/metrics, and resiliency.
Spring Boot Microservices - Spring Cloud API Gateway

Reference official page: Spring Cloud Gateway 

6. What is Spring Cloud Config Server?

This Spring Cloud Config Server module is used to externalize the configuration of our microservices into a centralized place.

If there are any changes in the configuration, our applications should be updated without the need to restart them.

There are many options to implement this Centralized Configuration eg: Using a Git Repository, or using HashiCorp Consul, etc.

Refer official page to know more: Spring Cloud Config

Watch my YouTube video to understand how Spring Cloud Config server works:

7. What is Spring Cloud Circuit Breaker?

Inter-service Communication is common in the Microservice architecture, if one of the services is down, the other service which is communicating with it should be able to handle this failure gracefully. 

Spring Cloud provides Spring Cloud Circuit Breaker module to implement the Circuit breaker pattern in the Microservices project.

Spring Cloud Circuit breaker provides an abstraction across different circuit breaker implementations. It provides a consistent API to use in your applications allowing you the developer to choose the circuit breaker implementation that best fits your needs for your app. 

Supported Implementations 

  • Resilience4J 
  • Spring Retry
Refer official page to know more: Spring Cloud Circuit Breaker

Watch my YouTube video to understand how Circuit Breaker Pattern works:

8. What is Spring Cloud Bus?

This module contains a lightweight message broker implementation, which is mainly used to broadcast some messages to the other services

Refer official page to know more: Spring Cloud Bus

9. What is Spring Cloud Sleuth?

Spring Cloud Sleuth provides Spring Boot auto-configuration for distributed tracing.

In Microservice Architecture, if there is any error, it’s hard to debug and trace it, Spring Cloud Sleuth provides us with the functionality to trace the inter-service calls.

Refer official page to know more: Spring Cloud Sleuth

10. What is Spring Cloud Stream?

This module mainly allows us to implement asynchronous communication between our microservices using event-driven architecture. 

We can use Apache Kafka or RabbitMQ as a message broker to implement event-driven microservices.

Refer official page to know more: Spring Cloud Stream

11. What is Spring Cloud OpenFeign?

Feign is a declarative web service client. It makes writing web service clients easier. 

To use Feign create an interface and annotate it. It has pluggable annotation support including Feign annotations and JAX-RS annotations. 

Feign also supports pluggable encoders and decoders. Spring Cloud adds support for Spring MVC annotations and for using the same HttpMessageConverters used by default in Spring Web. 

Spring Cloud integrates Eureka, as well as Spring Cloud LoadBalancer to provide a load-balanced HTTP client when using Feign.

Check out the complete example: Spring Cloud OpenFeign

12. Name Some of the Commonly used Spring Cloud annotations?

Here are the commonly used Spring Cloud annotations:
  • @EnableCircuitBreaker 
  • @EnableConfigServer 
  • @EnableEurekaServer 
  • @EnableFeignClients
  • @FeignClient(name=”ApplicationName”)

Annotations On Fault Tolerance provided by Resilience4j:
  1. @RateLimiter
  2. @Retry
  3. @CircuitBreaker
  4. @Bulkhead
  5. @Timelimiter

13. Name Commonly used Spring Cloud Modules to Build Microservices Projects?

Check out all Spring Cloud modules: https://spring.io/projects/spring-cloud

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