Software Development

Microservices Interview Questions and Answers

In this post we will take an overview of most important questions regarding the Microservices from basic to depth which will help you in cracking any difficult interview. So, there is no need to worry for your next interview test, because Java Code Geeks are here for you!

Almost all the question and answer that may be requested are listed and discussed below in detail. Microservices interview questions will lead you through the whole Microservices ecosystem and offers a comprehensive knowledge of the paradigm using the solution. We classify the questions to give information relevant to each module. We make sure that you do not have to think hard in an interview on Microservices.

Table of Contents

Basics Of Microservices

1. What is Microservices?

Microservices is an sculptural type subtype of service-oriented architecture (SOA) that constructs an application as a collection of services that are loosely coupled. Services must be great-textured and guidelines must be compact in a microservice architecture. The advantage of breaking down an application into various smaller services is how it enhances modifiability and makes it much easier to recognize, design and implement the application. This also develops mutability by allowing a small independent teams to separately create, configure and measure their differing services. It also enables an individual service’s aesthetics to arise via constant modularizing. Architectures predicated on microservices allow continuous integration and deployment.

2. What are Microservices and its architecture?

In software development, Microservices is an architectural trend used to comprise several of the small services. Furthermore, each microservice is limited to one single corporate app. Together all these micro-services construct a larger or more complicated application that satisfies the overall industry requirement. The most obvious design elements in the microservices include flexible or adaptable, scalable, loose coupling, composable, corporate, componenised, distributed, decentralized.

3. What are the advantages of Microservices Architecture?

  • With the support of their individual functionalities and services, microservice architecture can be formed and dispatched autonomously in any application.
  • The program still works even if one of the application’s services stops working.
  • Various languages and advancements can be used to construct the different services for the same program.
  • Instead of leveling all the modules at once, individual modules can also be adjusted as per the needs.

4. What are some important characteristics of Microservices?

  • It is possible to detach the services in the system application so that the entire application can be constructed, adjusted and modified as a whole.
  • Microservices modules are viewed separately and can therefore be readily switched and upgraded.
  • Microservices are incredibly easy because they demonstrate the ability of a single company.
  • Microservices give software developer teams sovereignty to operate independently from each other, that enables to accelerate.
  • It causes continual launches of computer software using deliberate mechanisation to create, measure and approve computer software.
  • Microservices treat software applications as responsible brands rather than concentrating on applications as projects.
  • Without reliing on interoperability, Microservices utilizes the right equipment.
  • Microservices enables rapid development and rejection of functionality.

5. What are the different features of Microservices application?

This is the fundamental question asked during the microservices interview. Below are the various features that Microservices supports:

  • Continuous Development: The two primary streams of continuous development that drive periodic launches and application deployment, include continuous integration and development.
  • Component-based: It is possible to easily upgrade, modify or supplant each microservice with the appropriate equivalent element.
  • Loosely Coupled: This allows the device to be constructed quickly and efficiently and helps to produce brands more quickly.
  • Scalability: Scaling the application for the amount of subscribers is simpler.

6. What is a Gateway in microservice?

Customers don’t call on microservices directly, they go via the Gateway. The Gateway calls the microservices and returns the answer to the customer. The Gateway separates the customer’s microservices. It also offers authentication, logging, load balancing and so on.

7. How do you monitor microservices?

The Spring Boot Controller is a decent instrument monitor statistics for individual microservices. However, it is hard to track them independently when you have multiple microservices. We could use opensource tools such as Prometheos, Kibana or Graphana for this purpose. Prometheous is a pull-based surveillance tool. It contains, shows and can activate notifications at certain intervals. Kibana or Grafana are dashboard instruments for data visualization and surveillance. As there are many dependencies in microservices, AppDynamics, Dynatrace and New Relics can be applied, which pull dependence between microservices.

8. How will you define the concept of Microservices?

Microservices structures an application in an style of architecture as a collection of little self-contained services that fit into a corporation profession. Usually you begin with just a little block and can create a bigger application together. The units are then organised in a sequence that later structures a tougher part of the bee hive. So each unit is attached but autonomous and can be adjusted according to prerequisites. This implies that harm to a unit does not impact an another unitʻs productivity. This allows destroyed unitʻs to be rapidly recreated and an software could do the same kind of.

9. When designing Microservices, what are the best practices to follow?

These are the industry standards each programmer must follow in the design of Microservices:

  • Every microservice will often keep the information store separate.
  • When designing Microservices it is important that the code must be organised at the same intelligence level.
  • For each Microservice, a separate development should also be designed.
  • We should make sure that each development should be used in containers.
  • While designing the microservices it is always necessary to treat the server as stateless.

10. Explain the major components of a Microservices Architecture

The following are the principle components of a Microservice architecture are discribed as follows:

  • Clients: Various subscribers send queries from various devices.
  • Identity Providers: It can configure user information and provide users with service tokens.
  • Static Content: It enables to store the entire system functionality for longer periods.
  • API Gateway: This gateway works along with several queries.
  • Management: It will balance Services over endpoints and missteps will also be identified.
  • CDNs: The content delivery network is a distributed network of proxy servers and their respective data centers.
  • Service Discovery: This will actually find the path of communication between the various Microservices.
  • Remote Services: It will allow remote access to network or other IT devices information.

11. What Is Spring Cloud?

Spring Cloud is a system for integrating with external systems in Microservices. It is a short – lived paradigm which quickly designs an application. It has a really vital role in Microservice architectural design in connection with the limitless amount of information processing. Spring cloud offers a certain degree of actual experience in standard use cases as well as a series of comprehensive functionalities below this:

  • Versioned and distributed configuration
  • Discovery of service registration
  • Service to service calls
  • Routing
  • Circuit breakers and load balancing
  • Cluster state and leadership election
  • Global locks and distributed messaging

Getting into micro-service implmentation

12. What Is Spring Boot?

Spring has become much more complicated with the additional features introduced. If you begin a new project, adding a new building path or Maven dependencies is necessary. Simply put, you must do all from scratch. Spring Boot is the answer for preventing all code settings. The ingredients may be considered spring when you cook a dish. When you cook a dish, it is fair to accept the ingredients as spring. The entire cooked dish is Spring Boot.

13. Explain three types of Tests for Microservices

In Microservices architecture tests are categorized into three wide types:

  • We can conduct a particular test such as quality and unit tests at the lower level test. Such tests are fully automated.
  • We can conduct exploratory tests at the mid – level, such as stress tests and accessibility tests.
  • We can perform acceptance tests at the highest level that are mainly less numerical. It enables investors to understand the various software characteristics.

14. What are the challenges you face while working Microservice Architectures?

It is easy to develop a lot of smaller microservices however the obstacles they sometimes face were as follows:

  • Automate the Components: Hard to optimize as a variety of small modules are available. We will have to adopt the building, deployment and monitoring phases for each module.
  • Perceptibility: It is hard to deploy, preserve, supervise and address troubles to keep a huge number of modules together. All modules need to be highly perceptible.
  • Configuration Management: It is often difficult to maintain the configurations for modules in different environments.
  • Debugging: Every service is difficult to find for a mistake. Centralized logging and workflows are crucial for debugging issues.

15. Shed light on the basic need of Microservices in today’s context of application development

In the field of software development, micro services are also recognised as a new pattern. It has taken on importance because it can increase efficiency and speed. It is also able to efficiently maintain software and services. Some people also call it a method and culture solution that gives greater business performance. It actually plays an extremely vital role in today’s software development, as it is able to be deployed efficiently in the production of a monolithic application.

16. Which DB is preferred by Microservices based Architecture?

Database selection affects the form of microservice information to be stored in the database. So, Ephemeral, transactional, transitional and operational data are the main four types of data that are stored. When choosing or selecting a database type, consider the data storage quantity and duration. Also assume the microservices ‘ quality and throughput requirements.

17. Why Would You Need Reports & Dashboards In Microservices?

Most of the reports and dashboards were used for monitoring and maintaining microservices. Multiple options are available to help support this motive. It is possible to use reports and dashboards to:

  • Find out which resources are exposed to microservices.
  • Find out which services are affected whenever module alterations take place.
  • Provide an instant access point anytime information is needed.
  • Provides information about the versions of the deployed components or modules.
  • To give the components a level of self awareness and compliance.

18. How Does PACT Work?

PACT is an tool that is open source(freely available). It enables to exam customer and service provider relationships. It isn’t included in the lease, however, greatly increasing the application’s reliability. The customer service developer begins by writing a test that characterizes how the service provider interacts. The test involves the status of the supplier, the application body and the predicted response. PACT generates a photocopy against which the test is performed on the basis of it. Store the output in a JSON file.

19. What is Coupling and Cohesion?

The coupling can be seen as the intensity calculation between the module reliance. A fine software design for Microservices often comprises of high cohesion and low coupling. When you are asked questions of microservices, it is important to remember that a structure of low coupling alongside high cohesion is an essential component in designing microservices. A service understands very little about another when it is loosely coupled. The services are therefore preserved. All pertaining reasoning can be maintained in a service in a higher level of cohesion. In other cases, the services will attempt and influence overall quality to interact with each other.

Advanced Microservices questions

20. How Would You Perform Security Testing of Microservices?

Explain to the interviewer before responding to this question about the microservices that microservices can not be fully tested. You have to test the parts on your own. There are three popular methods:

Code scanning – To make sure that every code line is bug – free and replicable.

Flexibility – In order to be adaptable to system requirements, the security measure should be flexible.

Adaptability – In order to address the new problems from spammers or security breaches, safety procedures should also be adaptable and upgraded.

21. What Are Some Major Roadblocks For Microservices Testing?

  • Before beginning to type test cases for integration testing, testers ought to have a comprehensive knowledge of all incoming and outgoing processes.
  • When autonomous teams actually work on unique features, cooperation can be a very difficult task. A time – door for complete regression testing can be difficult to find.
  • The complexity of the system also increases with an increased number of microservices.
  • Testors should make sure no disturbance between the information exchange between the modules while transitioning from monolithic architecture.

22. Why Do People Hesitate In Using Microservices?

  • Requires heavy investment – A lot of cooperation is required for microservices. Your teams should be able to update too well at times as they operate independently.
  • Heavy architecture set up – The entire system is usually spread, the architectural style is strong.
  • Excessive planning for handling operations overhead – If you intend to use Microservices architecture, you must be prepared for overhead operations.
  • Autonomous staff selection – Qualified experts are required to provide full support for heterogeneous microservices.

23. What Is Semantic Monitoring?

The entire application is monitored and computerized tests are combined. Semantic Monitoring’s principal advantage is to discover out the qualities that make your business much more profitable. After a problem has been detected, it allows for faster insulation and bug triage, reducing the main repair time. After a problem has been detected, it allows for quicker insulation and bug emergency care, lowering the primary maintenance time. It tries to identify the transfers which are impacted by availability or lack of quality.

24. How can we separate Deployment from Release of Microservices?

Two distinct MicroServices events are Deployment and Release. Blue / green deployment is one way to do this. Two variants of a Microservice were deployed simultaneously in this case. However, only one version actually makes genuine demands. After we have examined the other version well though, we switch the versions. In order that the functionality runs properly in freshly dispatched versions, we may run a smoke test suite. The new version could be published live based on the outcome of the smoke test.


25.What is the difference between Authentication and Authorization?

Authentication: Before disclosing confidential information, the authentication system defines the identifying of the user. It is very important to preserve the sensitive information for the system or interfaces, where the user has the priority. The user then claims the identity of an person (his or her) or of an organisation. The username, password, fingerprint, etc might be the credentials or claims. The application layer deals with authentication and non-repudiation, kind of problems. The inefficient method for authentication might greatly impact the service’s availability.

Authorization: The authorization method is being used to determine exactly which authorizations an authenticated user is granted. The authorisation is given when the identity of the user is guaranteed before, then by checking up the entries stored in the tables and databases, the user access list will be established. The authorization is given when the identity of the new user is guaranteed before, then by checking up the entries stashed in the tables and databases, the permissions list will be established.

26. What is Bounded Context?

Bounded context in the field of domain driven design is a central pattern. DDD’s tactical design segment focuses on the treatment of huge models and teams. DDD addresses huge models by splitting them into different boundary contexts and making their interactions explicit. DDD deals with product design predicated on domain models. A model serves as an UbiquitousLanguage to enable interaction among software engineers and field professionals. Also it behaves as the abstract base for the computer software itself and the way in which it is divided into objects and functions. In order for a system to be efficient, it has to be unified-internally coherent to avoid contradictions.

27. What is a Consumer Driven Contract (CDC)?

Each consumer catches up with its supplier’s expectations in a separate contract in consumer-driven contracts. All these contracts are shared with the provider to provide an insight into the obligations that each individual customer has to fulfill. To validate these obligations, the provider can create a test suite. To validate such obligations, the provider can develop a test suite. This allows them to remain agile and to make changes which do not affect consumers, as well as to identify consumers who will suffer the necessary changes for further planning and debate. Pacto helps to ensure that such commitments are fulfilled and decouples implementation obligations, so that customers and suppliers can be autonomously tested. For their testing, suppliers can also decouple consumers. Pacto may use contracts for provider testing to visualize consumers.

28. How can we do cross-functional testing?

The verification of non-functional requirements is a cross-functional test. These prerequisites are system features which can not be enacted as normal. For instance. Cross-functions testing relates to cross-functional requirements. The number of simultaneous system-endorsed users, site usability, etc. Commercial users often do not initially determine cross-functional requirements. However, they expect these when software is finished and used for development. In the original stage of the project itself, it is always a good question to ask companies about these cross-functional expectations.

29. Why do we use Correlation IDs in Microservices architecture?

The correlation ID is a single value connected to requests and messages that refer a specific transaction or event chain. A correlation ID is also known as a transit ID. A well publicized pattern of enterprise integration depends upon the use of Correlation ID. A correlation ID forms part of Java Messaging Service (JMS) as the non-standard HTTP header. But again, it is ambiguous to attach a correlation ID to a request. There’s not one you have to use. But you’re going to do enough to use a correlation identifier in your messages if you model a distributed system that utilizes messages delays and asynchronous processing.

30. What is Confused Deputy Problem in security context?

Assume that the customer sends the server name of the input and output file. The server builds and stores the input file in the output. Assume, too, the customer has fewer privileges than the server. Now also suppose there is a “restricted” file where the server doesn’t have authorization from the client. At that point, the server compiles the file and then write the server into a “restricted” file that overwrites the preceding content if the user sends an absurd input and a “restricted” as output file. The client had no “restricted” authorization here, but the server did. The server is thus an administrator who has been used for a manipulative action. Such problems are known as Confused Deputy Problem.

31. What is PACT?

The Pact is a testing tool for contracts. Contract testing provides services (such as an API provider and a customer) with the possibility of communicating with each other. The only way to determine that services can interact is through the use of costly and fragile integration tests without contract testing.

32. What is Conway’s law?

Conway’s law shows that the design of every system is impacted substantially by the communications system of the organisation. The law is widely related to software development but applies to systems and organisations.

33. What are Client certificates?

The certification of customer verification is used for a SSL handshake to authenticate customers. It authorize users who access a server through a customer authentication certificate exchange. This ensures that the customer is who he claims to be. This ensures that the customer is who he claims to be. This deletes unverified entries in the user user profile of a database when an Internet user authenticates the server.

33. How Do You Override a Spring Boot Project’s Default Properties?

We can do this by defining the  properties in the file. For instance, you should determine the suffix and prefix for Spring MVC applications. The following properties can be entered in the file.

  • For suffix – spring.mvc.view.suffix: .jsp
  • For prefix – spring.mvc.view.prefix: /WEB-INF/

34. What is the Role of the Spring Boot

This is one of the most essential features that enables you to obtain the present state of a development application. The current status can be monitored using multiple metrics. It also provides parameters for RESTful Web services that can be used simply to check the various statistics.

35. How Is Spring Security Implemented In a Spring Boot Application?

For implementation, minimum setup is necessary. Just add the jump-boot-starter-securitystarter to the pom.xml file. You also have to generate a Spring configuration class to bypass the necessary procedure while broadening the WebSecurityConfigurerAdapter for protection in the application.

36. Embedded Containers That are Supported by Spring Boot

Deployment can be carried out by two methods whenever you create a Java application:

  • Use an external application container.
  • Inside your jar file embedding the container.

The jetty, tomcat, and undertow servers are all included in Spring Boot.

  • Jetty – The Eclipse Jetty can be integrated into frames, application servers, methods and clusters in a broad variety of projects.
  • Tomcat — The JavaServer Pages free and open source is a very well – functioning JavaServer integration with embedded software.
  • Undertow – A durable and popular web server that develops a web server using tiny single handlers.

37. What Do You Mean by End-To-End Testing of Microservices?

End – to – end testing checks whether it all actually works as planned. all workflow procedures are validated. Also it guarantees that perhaps the system is working uniformly and thus fulfills the business objectives.

38. What Is OAuth?

OAuth enables easy access customer programs using third party service such as Facebook, GitHub, etc. via HTTP by open authorization protocol, otherwise regarded as OAuth. Without the need for credentials you can share data among various sites. OAuth enables a third-party such as Facebook to use the account details from the end user while maintaining it safe (never using or displaying the login information of the user). It behaves much more on behalf of the subscriber as an middleman while giving the server a token to access the data requested.

39. Why Do We Need Containers for Microservices?

For handling a Microservices based application, containers are the simplest way to do it. The user can be deployed and developed individually. In the image of a container, you may also use Docker to hide microservices. Microservices can use these features without any additional dependencies or effort.

40. What Are the Ways to Access RESTful Microservices?

One of the commonly asked question in the Microservices interview is how to access RESTful Microservices. There are two ways to do it which are as follows:

  • Use a REST template that is load balanced.
  • Use multiple microservices.

41. Common Mistakes Made While Transitioning to Microservices

Often errors happen on the manufacturing process side as well as on development. But any experienced questioner will also have interview questions in the queue for microservices. Some common issues are:

  • The developer often fails to detail the difficulties at hand.
  • The rewriting of existing programs.
  • Not clearly delineated responsibilities, timeline and limits.
  • The scope of automation almost from the beginning has not been implemented and identified.


Those were the most important questions regarding the Microservices. These questions have been answered with the aim to make your interview easier. However, there is always more to explore.

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Last updated on Oct. 8th, 2021

Abhishek Kothari

Abhishek is a Web Developer with diverse skills across multiple Web development technologies. During his professional career, he has worked on numerous enterprise level applications and understood the technological architecture and complexities involved in making an exceptional project. His passion to share knowledge among the community through various mediums has led him towards being a Professional Online Trainer, Youtuber as well as Technical Content Writer.
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