50 Microservices Architecture Interview Questions Answers for Experienced Developers

Essential patterns, trade-offs, and system design scenarios for senior developers

Hey folks, in the last few years, Microservices has quickly become the darling architecture of many tech companies, so much so that everyone is following Microservices.

I have been doing Software Development for a long time, so I know things have changed from development to deployment, and Microservices is the next chapter on that.

I remember once I was asked this question: “Two microservices, A and B, share the same database for some entities due to legacy design. Microservice A makes a change to the entity, but Microservice B does not reflect the change immediately, leading to inconsistent behavior.

How would you refactor the system to solve the shared database issue without creating downtime?”

That was my first taste of Microservice interview questions. Ever since then, I have asked multiple different questions from basic to advanced level, which I am going to share in this article.

By the way, if you are new to Microservice architecture or just want to revise key Microservice concepts and looking for resources then here are a few online courses you can join:

Master Microservices with Spring Boot and Spring Cloud [Udemy]

Building Scalable Java Microservices with Spring Boot [Coursera]

Developing Microservices with Spring Boot [Educative]

Master Microservices with Java, Spring, Docker, Kubernetes [Udemy]

However, if you prefer watching YouTube videos, then I also suggest you first watch this 4-minute video on Microservices from ByteByteGo, to learn what Microservices are and When Not To Use Them.

Microservices are nothing but a small program that does one thing and does it well, much like a class. Contrary to Monolith, where all of your app functionality resides inside one application, Microservices split them into multiple services

For example, you can have a Microservice for authentication and authorization in your application, one Microservice for handling order flow, and another one for Users and so on.

In recent years, demand for Microservices has grown a lot, but it is not a silver bullet; it has its pros and cons, much like anything else in Software Development.

But many people in tech are busy breaking their monolith and making the same mistake. I am not a big fan of Microservices, especially if they are small, dependent on others, and there are in them 100s.

Instead, I like to be pragmatic and create more modular Microservices than smaller ones, kind of Mini Services

The problem is that when you have to be in a system, you have to follow system rules, and that’s why you also need to prepare for Microservices architecture and application development if you want to get the Java developer job you want

In the past, I have shared many questions for Java developer interviews, like these 35 Java Interview Questions, Spring Framework Interview Questions, and System Design Questions, and today, I am going to share a few more questions for you to practice.

I have divided the article into 3 sections. The first one discusses common questions on Microservices architecture. In the second section, we will revisit interview questions on Microservice Design Patterns and principles, and in the last section, we will see more advanced Microservice questions for experienced developers.

20 Basic Microservices Architecture Interview Questions

Here are common Microservices Interview Questions, which are based on general Microservices knowledge, and you must know them to use Microservices in your project.

1. What is a Microservices architecture, and how does it differ from a monolithic architecture?

Microservices, as the name suggests is a small services (a Java, .NET, JavaScript, or any other program) that provide a specific functionality. For example, the Authentication Service can provide authentication functionality and UserService can provide all the functionality related to Users.

2. What are the benefits and drawbacks of a Microservices architecture? Pros and Cons?

Microservices architecture is an approach to building software systems that involves breaking down a monolithic application into a set of small, modular services that can be developed, deployed, and scaled independently. Here are some of the benefits and drawbacks of this approach:

Pros of Microservices:

• Flexibility: Microservices architecture allows for flexibility in terms of technology choices, as each service can be implemented using different languages, frameworks, and databases. For example, you can implement one microservice in Java and another in C++ or Python.

• Scalability: Microservices can be scaled independently, which allows for better resource utilization and faster scaling of the overall system. With Cloud computing, Kubernetes can scale Microservices very easily depending on load.

• Resilience: Microservices architecture allows for more fault-tolerant systems, as a failure in one service can be isolated and handled without affecting the entire system.

• Agility: Microservices architecture allows for faster development and deployment cycles, as changes can be made to a single service without impacting the entire system.

• Reusability: Microservices can be reused across multiple applications, which can result in cost savings and increased efficiency.

Drawbacks:

• Complexity: Microservices architecture can increase the complexity of the system, as there are more moving parts and more interactions between services.

• Testing and Debugging: Testing and debugging a Microservices architecture can be more complex, as it requires testing each service individually, as well as testing their interactions.

• Monitoring and Management: Microservices architecture requires more monitoring and management, as there are more services to keep track of and manage.

• Inter-service communication: Microservices architecture increases the number of network calls between services, which can lead to increased latency, and if not handled properly, to cascading failures.

• Security: Microservices architecture can make it more challenging to implement security measures, as each service may need to be secured individually.

In conclusion, Microservices architecture offers many benefits in terms of flexibility, scalability, and resiliency, but it also increases the complexity of the system and requires more monitoring and management.

It’s important to weigh the benefits and drawbacks and choose the right approach that fits the specific requirements and constraints of your system.

And, if you want to watch, here is also a nice video from ByteByteGo, to learn the 5 most used Software architecture patterns, most of the questions will be from these patterns, particularly Microservices.

3. How to design and implement a microservice?

You can use any framework to develop Microservices in different programming languages, but in Java, you can use Spring Boot and Spring Cloud to implement Microservices.

4. What are the key characteristics of a well-designed Microservice?
Well-designed Microservices have clear, single responsibilities, are loosely coupled, have high cohesion, communicate via APIs, have bounded context, and are independently deployable, testable, and scalable.

And here are a few more Microservices questions for you to practice.

1. How to ensure that Microservices are loosely coupled and highly cohesive? Follow the single responsibility principle, use async messaging, avoid shared databases, and design around business capabilities rather than technical layers.

2. How can a Java Microservice and .NET Microservice talk with each other?
   Use REST APIs with JSON payloads or message queues - both technologies can handle HTTP requests and JSON serialization/deserialization natively.

3. How to handle cross-cutting concerns, such as security, in a Microservices architecture?
   Use an API Gateway for authentication/authorization, implement JWT tokens for service-to-service communication, and use sidecar proxies like Istio for encryption and policy enforcement.

4. Why is debugging so tough on Microservice Architecture?
   Distributed tracing is complex, requests span multiple services, logs are scattered across different systems, and reproducing issues requires coordinating multiple service states.

5. How to handle data consistency in a Microservices architecture?
   Use eventual consistency with event sourcing, implement the Saga pattern for distributed transactions, and avoid distributed ACID transactions across services.

6. How do you ensure that Microservices are scalable and resilient?
   Implement circuit breakers, use load balancers, design for horizontal scaling, apply retry mechanisms with exponential backoff, and isolate failures using bulkhead patterns.

7. How to handle service discovery and registration in a Microservices architecture?
   Use service registries like Consul, Eureka, or Kubernetes native service discovery, with health checks and automatic deregistration of failed instances.

8. How to handle service communication and data sharing in a Microservices architecture?
   Use REST APIs for synchronous communication, message queues for async communication, and avoid direct database sharing - each service owns its data.

9. How to handle service versioning and backward compatibility in a Microservices architecture?
   Use semantic versioning, implement API versioning strategies (URL path, headers, or content negotiation), and maintain backward compatibility during transitions.

10. How to monitor and troubleshoot Microservices?
    Use distributed tracing tools like Jaeger, centralized logging with correlation IDs, metrics collection with Prometheus, and service mesh observability features.

11. How to handle deployments and rollbacks in a Microservices architecture?
    Use blue-green deployments, canary releases, feature flags, and containerization with orchestration platforms like Kubernetes for automated rollbacks.

12. How to handle service governance and lifecycle management in a Microservices architecture? Use API gateways for policy enforcement, implement service contracts, use schema registries, and maintain service catalogs with clear ownership and SLAs.

13. How to handle security and access control in a Microservices architecture? Implement OAuth2/JWT for authentication, use RBAC for authorization, encrypt service-to-service communication, and apply zero-trust networking principles.

14. How do you handle data integration and data migration in a Microservices architecture? Use event-driven architecture for data synchronization, implement CDC (Change Data Capture), and use the Strangler Fig pattern for gradual migration from monoliths.

15. How to handle service composition and orchestration in a Microservices architecture? Use the API Gateway pattern for composition, implement the Saga pattern for orchestration, or use event choreography for decentralized coordination.

16. What Java Frameworks can you use to create Microservices?
    Spring Boot for rapid development, Quarkus for cloud-native performance, and Micronaut for low memory footprint and fast startup times.

17. How many Microservices do you have in your project? How do you find out if a user says that one of his orders is missing in the database?
    Use distributed tracing with correlation IDs across all services involved in the order flow, check event logs, and query each service's database independently, since each microservice owns its data.

18. How do you deploy your Java Microservices?
    We use Docker and Kubernetes for deploying our Microservices in the cloud. Docker is used to create a Docker image of the whole service, and then Kubernetes is used to deploy it on AWS or Azure. Service is managed by K8 so it takes care of starting stopped instances and increasing them if the load is increased

19. How to handle service resiliency in case of failures?
    K8 does that for you and starts a new MicroService or restarts the same one.

15 Microservices Interview Questions on Design Patterns and Principles

Here are a few more questions that are based on Microservices Design patterns and principles like API Gateway, CQRS, SAGA, and more.

1. What is the API Gateway pattern, and how is it used in Microservices architecture? Please explain what problem it solves and whether it’s mandatory for Microservices or not.

API Gateway is one of the essential microservice patterns that is used to provide a single entry point for external consumers to access the services. It acts as a reverse proxy and routing layer, which is responsible for request routing, composition, and protocol translation, among other things.

The API Gateway pattern solves several problems in Microservices architecture:

• It decouples the external consumers from the internal implementation of the services. This allows the services to evolve and scale independently, without affecting the external consumers.

• It provides a single entry point for external consumers, which simplifies the client-side service discovery and reduces the number of network calls.

• It can handle cross-cutting concerns such as security, rate limiting, and caching at the edge of the architecture, rather than scattering them across the services.

• It can aggregate multiple services into a single response, reducing the number of network calls and improving the performance of the client-side.

• It can handle protocol and content type translations, allowing the services to be implemented using different protocols and data formats.

It is not mandatory for Microservices architecture, but it is commonly used to help manage the complexity and improve the performance of Microservices. It can also be used to provide consistent security, rate limiting, and caching policies across the Microservices.

It’s worth noting that, depending on the size of your Microservices environment and the number of requests, it may make sense to have multiple API Gateways in order to distribute the load and improve scalability.

And, if you like to watch, here is a nice video from ByteByteGo which explains the API Gateway design pattern in Microservices:

2. Can you explain the Circuit Breaker pattern and how it is used to handle service failures in Microservices architecture? What problem does it solve?

It improves Service availability. Circuit breaker pattern is a technique used to prevent cascading failures by temporarily preventing further calls to a service that is failing frequently. It helps to improve the resiliency of the system.

3. What is the Command Query Responsibility Segregation (CQRS) pattern, and when is it appropriate to use it in Microservices architecture?

CQRS stands for Command Query Responsibility Segregation. It’s one of the popular Microservices design patterns that separates the read and write operations in a system and allows them to evolve independently. It allows for a more scalable and performant system, but also increases complexity.

And, if you want to watch, here is another great video from ByteByteGo which explains common distributed system design patterns, including CQRS in Microservices:

4. What is a retry pattern in Microservices? When and how to use it?

Retry pattern is a technique used in Microservices architecture to handle service failures automatically. It involves automatically retrying a failed service call a certain number of times, with a delay between retries.

This pattern helps to improve the robustness and resiliency of the system by increasing the chances of a successful call, even in the presence of temporary failures.

It’s also used to handle flaky service dependencies gracefully, by retrying the calls to them instead of breaking the whole process and returning an error.

Here are a few Microservices design patterns and principles-based questions for practice:

• Can you explain the Event-Driven pattern?
  Services communicate asynchronously through events published to message brokers, enabling loose coupling and better scalability by decoupling producers from consumers.

• Can you explain the Service Registry pattern?
  A centralized database that stores service locations and health status, allowing services to discover and communicate with each other dynamically without hard-coded endpoints.

• Can you explain the Sidecar pattern?
  A helper service is deployed alongside each microservice to handle cross-cutting concerns like logging, monitoring, and security without modifying the main service code.

• What is the Service Mesh pattern and how is it used in Microservices architecture? An infrastructure layer that manages service-to-service communication using sidecar proxies, providing features like load balancing, security, and observability transparently.

• What is the Back-end for Front-end pattern, and how is it used in Microservices architecture?
  A dedicated backend service for each frontend (mobile, web, IoT) that aggregates and transforms data from multiple microservices to match specific client requirements.

• What is the Bulkhead pattern?
  This pattern isolates critical resources (thread pools, connections, memory) to prevent cascading failures, ensuring that problems in one area don't bring down the entire system.

• What is the Saga pattern? What problem does it solve?
  Saga pattern manages distributed transactions across microservices using a sequence of local transactions with compensating actions, solving the problem of maintaining data consistency without distributed locks.

• Can you explain the Outbox pattern in Microservices architecture?
  This pattern ensures reliable event publishing by storing events in the same database transaction as business data, then publishing them asynchronously to avoid dual-write problems.

• Can you explain the External Configuration pattern and how it is used in Microservices architecture? Stores configuration data outside the service deployment package in centralized config servers, enabling dynamic configuration changes without redeployment across environments.

• What is the Strangler pattern?
  This pattern gradually replaces legacy monolithic systems by incrementally routing traffic to new microservices while keeping the old system running until fully migrated.

15 Advanced Microservices Interview Questions for Experienced Developers

These are more advanced questions on Microservices for experienced Java developers with 5 to 10 years of experience, and they cover advanced topics like data replication, data partitioning, Orchestration and service choreography, Security, etc.

• How do you handle data partitioning and data replication in Microservices?
  Use database sharding for partitioning and implement read replicas with eventual consistency, ensuring each microservice manages its own data partitioning strategy.

• Have you done any service partitioning and service scaling in a microservices architecture? If not, how would you do it?
  Partition services by business domain boundaries and scale horizontally using container orchestration with auto-scaling based on CPU/memory metrics and request load.

• Explain service orchestration and service choreography in microservices. Orchestration uses a central coordinator to manage service interactions, while choreography allows services to react to events independently without central control.

• What challenges have you faced while developing Microservices in your project?
  Distributed debugging complexity, network latency issues, data consistency across services, service discovery management, and increased operational overhead.

• How do you handle service security and service encryption in microservices? Implement JWT tokens for authentication, use TLS for encryption in transit, apply mTLS for service-to-service communication, and store secrets in dedicated vaults.

• How do you implement service monitoring and service logging in a microservices architecture?
  Use centralized logging with correlation IDs, implement health check endpoints, deploy monitoring agents, and use observability platforms like Prometheus and Grafana.

• How do you handle service tracing and service debugging in a microservices architecture?
  Implement distributed tracing with tools like Jaeger or Zipkin, use correlation IDs across all service calls, and maintain centralized log aggregation.

• What is service testing and service quality assurance in a microservices architecture?
  Implement unit tests per service, contract testing between services, integration testing with test doubles, and end-to-end testing in staging environments.

• How do you handle service deployment and service rollback in a microservices architecture?
  Use containerization with blue-green deployments, implement canary releases, maintain rollback scripts, and use feature flags for quick service toggles.

• How do you handle service governance and service lifecycle management in Microservices Architecture?
  Establish API contracts, implement service versioning policies, use API gateways for governance, and maintain service catalogs with clear ownership.

• How do you handle service migration and service modernization in a microservices architecture?
  Apply the Strangler Fig pattern, implement gradual traffic routing, use feature flags for rollback safety, and migrate data incrementally.

• How do you handle service integration and service API management in a microservices architecture?
  Use API gateways for external access, implement service contracts, use message queues for async integration, and maintain API documentation.

• How do you handle service performance and service optimization in a microservices architecture?
  Implement caching strategies, optimize database queries, use connection pooling, apply circuit breakers, and monitor service metrics continuously.

• How do you ensure that your Microservice doesn't affect other Microservices on the same host?
  Use containerization for resource isolation, implement resource limits, apply the bulkhead pattern for thread pools, and use separate JVMs or processes.

• How do you organize your Microservices? Does all code stay in the same repo, or do you create multiple repos for different Microservices?
  Use separate repositories per microservice for independent deployment cycles, or a monorepo with clear module boundaries for shared libraries and easier refactoring.

• What is better? Different databases for different Microservices or a single database for all Microservices? Why?
  Different databases per microservice ensure data ownership, enable independent scaling, prevent coupling, and allow technology diversity, following the database-per-service pattern.

Java and Spring Interview Preparation Material

Before any Java and Spring Developer interview, I always used to read the following resources

Grokking the Java Interview: click here

I have personally bought these books to speed up my preparation.

You can get your sample copy here, check the content of it, and go for it

Grokking the Java Interview [Free Sample Copy]: click here

If you want to prepare for the Spring Boot interview you follow this consolidated eBook, it also contains microservice questions from spring boot interviews.

Grokking the Spring Boot Interview

You can get your copy here — Grokking the Spring Boot Interview

That’s all about the 50+ Microservices Architecture Interview Questions for Java developers. I have tried to include both basic and advanced Microservices questions for beginners and experienced developers.

Even if you have not worked extensively on Microservices, these questions can help you learn all the essential Microservices concepts very quickly.

Thanks for reading this article so far. By the way, if you are new to Microservice architecture or just want to revise key Microservice concepts and are looking for resources, then here are a few online courses you can join:

1. Master Microservices with Spring Boot and Spring Cloud [Udemy]

2. Building Scalable Java Microservices with Spring Boot [Coursera]

3. Developing Microservices with Spring Boot [Educative]

4. Master Microservices with Java, Spring, Docker, Kubernetes [Udemy]

This list includes both video and text-based courses as well as project-based courses for hands-on learning. You can join one or a couple of them to revise Microservices concepts.