Top 20 Microservices Interview Questions

Top 20 Microservices Interview Questions

Planning for questions you will be asked during an interview ranks as one of the top five(5) steps in preparing for a job interview. Recent research by the Nginx web server organization found out that most tech companies either implement their systems via microservices or are actively researching how to implement microservices. We will present Microservices Interview Questions here.

Microservices Interview Questions

To help you ace a Java microservice job interview, we have collated the top 30 interview questions and answers to help you prepare. 

  1. What are Microservices? 

Microservices are service-oriented application development architectures. This means an application is built as a collection of different services. Read more on microservices are and their benefits.

  1. What is monolithic architecture?

Monolithic architecture is the traditional way of developing applications. In this development architecture, the application is developed as just one service. This gives room to some overhead where for instance, if an application module is to be updated, the whole application will need to be updated. More faults in the monolithic architecture.

  1. Example of a microservice framework for java?
  • Spring boot
  • Micronaut
  • Ballerina
  • DropWizard
  • Eclipse Microprofile
  1. What is Spring cloud?

Spring Cloud provides integration tools for microservices and builds applications fast and efficiently. Spring cloud contains features like load balancing, circuit breakers, distributed messaging, amongst others.

Check the official documentation for more information

  1. What is RESTful?

REST stands for Representational State Transfer. REST defines a set of industry standards and protocols on how entities on the web should communicate. RESTful refers to entities on the web that obey these set of protocols and standards.

Read more on REST, RESTful, RESTful web services and REstful APIs

  1. Difference between Spring Cloud and Spring boot.

Spring boot and Spring cloud are both parts of the same framework, but they have different work requirements for java microservices. Some of their differences include;

S/NSpring BootSpring Cloud
1Makes microservices to increase productivityUsed to collect deployment configuration and manage itself
2Works mainly to maintain the traffic of the created networkThe main purpose is to reduce time and increase productivity
3Specifically built for cloud applicationsProduct ready application, spring web application
  1. Commonly used tools for Microservices.

These tools can be categorized under different stages of the microservice life cycle:

  • API management and testing: API Fortress, Postman, TYK
  • Messaging: RabbitMQ, Apache Kafka
  • Monitoring: Logstash, Graylog
  • Kube Development: Kubernetes, Telepresence 
  • Orchestration: Conductor
  • Programming: Java Spring boot, elixir
  • Toolkits: Google Cloud platform’s Cloud function, fabric8, Seneca
  • Architectural Frameworks: goa, Kong
  • Serverless tools: Apache Openwhisk, Claudia, Serverless,  Kubeless, IronFunction
  • With a host of other tools for team building 
  1. Role of actuators in Spring boot.

Actuators in spring boot are mainly used to expose operational information about the running application. This information includes things like health metrics, dumps, etc. Actuators make use of HTTP to allow for communication.

  1. What is the meaning of OAuth?

OAuth stands for open authorization. It is a protocol that helps to access a client’s application using third-party protocols. These third-party protocols include LinkedIn, Facebook, GitHub, Gmail, etc. OAuth allows for the transfer of resources between application endpoints without the need for authentication credentials.

  1. What are Client Certificates?

A client certificate is a type of digital certificate used by client systems on a network to authenticate requests made to a remote server. The opposite of client certificates is server certificates that work in the client certificates’ negative logical domain.

  1. What is the use of PACT in a microservice architecture?

PACT framework is an open-source implementation of consumer-driven contracts. They are simple JSON format files that define a standard for communication between microservices. PACT is, however, different from the contract made. PACT increases the reliability of the microservice application.

  1. What is the use of containers in microservice?

Containers are the most effective method to manage microservices. Containers help developers to deploy and test microservices in an isolated environment.

  1. What is CDC?

CDC means Consumer-driven contracts. These contracts ensure that developers create what the customer actually needs and not what the developer thinks the customer asked for. This definition is done through JSON files which defineJSON data format between consumer and developer. The data format agreement through json files is referred to as a contract. 

  1. How would you start a new Spring boot project?

This question has more than one answer. The best way would be to narrate the steps you go through when starting a new spring boot application. We will give steps on how to start a Spring boot project using the

  • Step 1: Use the to create a “web” project select the latest version of spring boot but not the snapshot. Head to the “dependency” dialogue and search for “web” click on it to add web dependencies to your new spring boot application. 
  • Step 2: Click the generate button, and a zip file will be downloaded.
  • Step 3: Unpack the zip file into a folder on your system
  • Step 4: Open the project in your preferred folder and locate the
  • Step 5: Add the code as seen below in the

package com. example.demo;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

Import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.RequestParam;

import org.springframework.web.bind.annotation.RestController;



public class DemoApplication {

public static void main(String[] args) {, args);



public String hello(@RequestParam(value = “name”, defaultValue = “World”) String name) {

return String.format(“Hello %s!”, name);



  • Step 6: Build and run the project

If you’re running a macOS/Linux issue, the command ./mvnw spring-boot: run If you are running the windows os, issue the following command mvnw spring-boot: define JSONrun. Your project will build and run. To access the running application, open your web browser and visit the link http://localhost:8080/hello.

Learn more about building spring boot microservices

  1. How do you override a spring boot default project properties?

Spring boot application’s default properties can be overridden by changing the properties in the application—properties to the preferred application property. For instance, it is required to specify the spring prefix and suffix property for a spring boot application. This can be done by entering the configuration values for the prefix and suffix property in the file as shown below:

  • For suffix – spring.mvc.view.suffix: .jsp
  • For prefix – spring.mvc.view.prefix: /WEB-INF/
  1. What is semantic monitoring?

Semantic monitoring combines automated testing procedures with full application monitoring processes. The main goal of this process is to determine the players/factors in the profitability of your business. 

  1. What are the embedded containers supported by Spring boot?

Java applications are deployed through two major strategies, either linking with an external container or embedding a container in the application jar file.

The embedded container supported by spring boot are only three(3) namely:

  • Jetty – jetty can be embedded in frameworks, application servers, tools, and clusters. It is used in a wide range of projects.
  • Tomcat – Tomcat is an open-source JSP (JavaServer Pages) implementation that works well with embedded systems.
  • Undertow – Uses single handlers to develop a web server. Undertow is small and prominent.
  1. Why do you feel people hesitate to use microservices?

There are more than a few answers to this question. Answering correctly can be based on experience in building microservices. The best thing to do would be to narrate a few bad experiences or pitfalls in create java microservices. However, few answers serve as a general issue across microservice developers regardless of working experience;

  • Cost Intensive: microservices require a lot of collaboration across multiple teams. This raises the need to synchronize efforts across the team. Investing in collaboration tools can prove highly expensive, and paying the cost of each team is an even greater expense.
  • Architecturally intensive: Microservices and the developers building these services require heavy architectural setup to function effectively. This means the organization has to invest heavily in both software and hardware architecture.
  • Expensive staff selection: Highly skilled staff are needed who can manage deployed microservices.

Combine these few points with whatever experience you have with developing microservices to answer this question.

  1. Define what you understand by DDD?

DDD means Domain-Driven Design. This is an application design strategy that focuses on core domain knowledge logic, finds complex designs on real-life models of the domain, and has a subject matter expert as part of the development team to constantly improve the microservices-based server application.

  1. How would you implement security in a Spring boot application?

To implement security on a spring boot application, minimal configuration is require, the steps include:

  • Step 1: Add spring-boot-starter-security starter to the pom.xml file
  • Step 2: Create a config file to override the required method while extending the webSecurityConfigurerAdapter
  • See some sample code on how to get this done 


import org.springframework.context.annotation.Configuration; 




public class SecurityConfig extends WebSecurityConfigurerAdapter {     


protected void configure(HttpSecurity http) throws Exception {         









.permitAll();     } }

Below are some links to help prepare for your interview. Good luck!


Also read Latest Microservices Interview Questions And Answers

Top 20 Microservices Interview Questions

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