Top Microservices Interview Questions and Answers (2023)

Microservices is an architectural concept that structures an application as a collection of services. In microservices, a single application is comprised of various loosely coupled and autonomous smaller services that can work on their own. This article, top microservices interview questions and answers.

Microservices or microservice architecture is a widely used architectural concept within software development. It is an approach for developing software systems that focuses on building single-function modules with well-defined interfaces and operations. More and more companies are moving towards a microservice architecture. It is an important skill to gain that can help you land a rewarding job. In this blog, we have listed the top microservices interview questions to help you prepare for your next job interview.

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Understanding Microservices

Microservices is an architectural concept that structures an application as a collection of services. In microservices, a single application is comprised of various loosely coupled and autonomous smaller services that can work on their own.

In simpler terms, Microservices is about breaking a big monolithic application that contains everything from UI to database into small pieces of applications that are loosely coupled and are independently deployable.

For example, Amazon has dismantled its monolithic applications and migrated to microservices. Their core application is composed of several independent applications to achieve greater business agility, profits, and scaling benefits. Let’s take a look at some of the advantages of microservices.

Benefits Of Microservices

• Independently deployable
• Loosely coupled
• Organized around business capabilities
• Highly maintainable
• Easy integration
• Easy to integrate with third-party services

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Top Microservices Interview Questions

Here are the most commonly asked Microservices interview questions and answers:

Q1. What are the features of microservices?

Ans. Some of the key features of microservices are:

• Decentralized Governance: Development teams have more control over choosing the right tool according to the goal.
• Isolation: Microservices are comprised of independent components. If one component fails, developers can use another service and the application will continue running independently.
• Decoupling: Since services are decoupled, the application can be easily created, modified, and scaled.
• Team autonomy: Developers can work independently. This results in a faster project timeline.
• Specialized: Each service focuses on solving a specific problem. If a service becomes complex, it can be divided into smaller services.
• Continuous Integration And Continuous Delivery: Microservices make it easy for developers to try out new ideas and roll back to the previous version if something doesn’t work.
• Black Box: The information about each microservice is hidden from other components.

Q2. What are the advantages and disadvantages of microservices?

Ans. The advantages and disadvantages of microservices are:

Advantages	Disadvantages
Independently manageable services	Hard to manage a large number of services
Faster development cycles	Difficult to maintain transaction safety
Better agility	Requires more collaboration
Greater scalability	Requires a proper corporate culture such as DevOps culture and automation practices
Isolated services	Difficult to test and monitor over a distributed environment as the architecture is complex
Lower cost of scaling compared to the monolithic architecture

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Q3. What are the components of microservices?

Ans. The core components of microservices include:

1. Clients
2. Identity Providers
3. API Gateway
4. Messaging Formats
5. Databases
6. Static Content
7. Management
8. Service Discovery

Let us understand each of the microservices elements in detail:

1. Clients: The first component in the microservices architecture is the clients. The client apps generally utilize functionality from more than one microservice. They handle multiple calls to microservice endpoints if that utilization is performed directly.

2. Identity Providers: The requests are forwarded to the identity providers who authenticate the requests and communicate the requests to API Gateway.

3. API Gateway: These are the entry points for the clients to forward requests to relevant microservices. It handles the request routing, composition, and protocol translation.

4. Messaging Formats: They communicate through 2 types of messages:

• Synchronize – clients wait for the responses from a service (microservices use HTTP protocol)
• Asynchronized – clients do not wait for the responses from a service (microservices use protocols such as AMQP, MQTT, STOMP)

5. Databases: Microservice has a private database to capture their data and implement the business functionality. The databases are updated through the service API.

6. Static Content: Now microservices deploy the static content to a cloud-based storage service. It sends them to the clients through Content Delivery Networks (CDNs).

7. Management: This element enables operations and business users to configure services in run-time.

8. Service Discovery: It helps find the route of communication between the microservices and maintains a list of services on which nodes are located.

Q4. Which embedded containers are supported by Spring Boot?

Ans. Some of the embedded containers are supported by Spring Boot are:

• Apache Tomcat: open-source JavaServer Pages implementation
• Eclipse Jetty: we can embed it in application servers, frameworks, tools, and clusters in different projects.
• Undertow: a flexible web server used to develop a web server with small single handlers.

Q5. What are Client Certificates in microservices?

Ans. Client certificates are digital certificates that help client systems make authenticated requests to a remote server. They help in many mutual authentication designs by offering strong assurances of a requester’s identity.

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Q6. Explain what is DRY in Microservices architecture?

Ans. DRY stands for Don’t Repeat Yourself. This principle states that every piece of knowledge must have a single, clear, and authoritative representation within a system. It supports reusing the code.

Q7. How can you eradicate non-determinism in tests?

Ans. We can eradicate non-determinism in tests using the following ways:

1. Asynchronous
2. Isolation
3. Time
4. Quarantine
5. Resource leaks
6. Remote Services

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Q8. Explain the use of PACT in microservices.

Ans. PACT is an open-source testing framework. This tool enables testing interactions between service providers and consumers. Here are the steps involved in PACT:

• Define the expected result on the Consumer side service
• Generate the PACT file
• Share the generated PACT file with the Provider service

Q9. Name some of the tools used for microservices.

Ans. Some of the tools used for microservices are:

• Docker
• Hystrix
• Wiremock

Q10. Explain OAuth.

Ans. OAuth refers to the Open Authorization protocol. It enables users to access the client applications on HTTP for third-party providers, like GitHub. Using OAuth, you can share information between services without exposing your password.

Q11. Name the different types of tests used in Microservices.

Ans. There are three main types of tests used in Microservices:

• Bottom Level Test
• Middle-Level Tests
• Top Level Tests

Q12. Explain CDC in Microservices.

Ans. In microservices, CDC stands for Consumer-Driven Contract. It is a method used for developing Microservices that can be used by external systems.

Q13. How to override a Spring Boot project’s default properties?

Ans. To override a Spring Boot project’s default properties, we will have to specify the properties in the application.properties file. We will need to specify the below prefix and suffice in the Spring MVC application:

• Prefix: mvc.view.prefix: /WEB-INF/
• Suffix: mvc.view.suffix: .jsp

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Q14. What do you mean by Service Registration and Discovery in Spring Cloud?

Ans. In microservices, adding and altering configurations becomes complex with the increase in the number of developed and deployed services. Service Registration and Discovery in Spring Cloud help handle various issues such as services going down that may arise due to manual changing

We typically run multiple instances of services. Thus, we need a mechanism to call other services without hardcoding their hostnames. Service Registration and Discovery play an important role in the same.

Q15. Explain smart endpoints and dumb pipes.

Ans. Smart endpoints and dumb pipes are design principles that support time-tested and asynchronous communication. Microservices communicate over the network. With the increase in the number of services, the risks due to unreliable networks also increase. Smart endpoints and dumb pipes help handle the service-to-service communication within a microservice architecture.

Q16. What is a serverless model?

Ans. A serverless model is one in which an organization does not need to invest in or maintain physical hardware. It can rely on a trusted third party to maintain the physical infrastructure, such as server, network, and storage. Using this approach, an organization can develop applications without needing to manage the required infrastructure.

Some of the popular third-party serverless platforms are:

• AWS Lambda
• Microsoft Azure
• IBM Bluemix/OpenWhisk

Q17. What are the differences between microservices and SOA Architecture?

Ans. The major differences between microservices and SOA are:

Microservices	SOA
It follows a share-as-little-as-possible principle	It supports the share-as-much-as-possible principle
Microservices hosts services that can function autonomously	SOA is designed to share resources across different services
Focuses on decoupling	Focuses on maximizing application service reusability
Does not involve component sharing	Involves component sharing
Deployment is quick and easy	Deployment is less flexible
Every service can have independent data storage	Services share data storage
Collaboration between teams is required	Uses common governance protocols across teams
Shared services – REST and JMS	Shared services – AMPQ and SOAP
Less scalable	Highly scalable

Q18. What are the differences between microservices and monolithic architecture?

Ans. The following are the differences between the two architectures:

Microservices	Monolithic
Collection of smaller independent units	Single unified unit
Smaller in size and thus, easy to manage	Large in size and hence, difficult to manage
Need to redeploy microservice that requires change instead of the entire application	Need to redeploy the entire application for any small change
Bug in a particular microservice does not affect other microservices and the entire system remains intact	A bug in any module affects and brings down the entire monolithic application.

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Conclusion

We hope these microservices interview questions will help you in understanding various concepts of microservices and prepare you for your next microservices interview.