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Microservices Design Patterns Interview Questions

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What Is Coupling And Cohesion

Microservices Design Patterns | Microservices Architecture Patterns | Edureka

The coupling can be considered to be the measurement of strength between the dependencies of a component. A good Microservices application design always consists of low coupling and high cohesion.

Following the previous question, often the interviewer will ask about cohesion. It is also another measurement unit. More like a degree to which the elements inside a module remain bonded together.

If you are appearing for microservices interview questions then it is imperative to keep in mind that an important key to design microservices is a composition of low coupling along with high cohesion. When loosely coupled, a service knows very little about other. This keeps the services intact. In high cohesion, it becomes possible to keep all the related logic in a service. Otherwise, the services will try to communicate with each other, impacting the overall performance.

Which Embedded Containers Are Supported By Spring Boot

Whenever you are creating a Java Application, deployment can be done by 2 methods:

  • You can also embed the container inside your jar file.

Spring Boot contains Jetty, Tomcat and undertow servers, all of which are embedded.

Jetty Used in a wide number of projects, Eclipse Jetty can be embedded in frameworks and application servers, tools as well as clusters.

Tomcat Apache Tomcat is an open source JavaServer pages implementation which works well with embedded systems.

Undertow A flexible and prominent web server that uses small single handlers to develop a web server.

Question: What Is A Ribbon In Microservices

Answer: Netflix Ribbon is part of Netflix OSS used for client-side load balancing. The ribbon is a cloud library and it automatically interacts with Netflix Service Discovery .

Ribbon provides the client-side load balancing algorithms. Ribbon provides control over the behavior of clients based on HTTP and TCP. It is to be noted that when Feign is used, Ribbon is also applied.

Ribbon supports features like

c. Multiple protocol support in Asynchronous model

d. Caching and batching.

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What Are Design Patterns

The interviewer may begin with this question as a warmup. How you answer can indicate how much experience you have on this topic. Briefly describe what you understand design patterns to be.

Example: Design patterns are extension codes used to solve common problems in the software development process, such as repetitive code, coding everything from scratch and adding extra properties or functions. These patterns save time and effort by employing dynamic aspects of object-oriented programming to allow user inputs to decide what outputs are displayed by rationalizing relationships between objects.

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Microservices Interview Questions And Answers For Software Engineers

Microservices in Java

Microservice architecture a variant of the service-oriented architecture structural style arranges an application as a collection of loosely coupled services. In a microservices architecture, services are fine-grained and the protocols are lightweight. Here is a list of coding interview questions on Microservices to help you get ready for your next data structures interview in 2021.

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Api Gateway Design Pattern

Let us take a look at this design pattern.

  • It is a design pattern that acts as a single point of contact for incoming requests, decides which microservice to send the request to get the data, and also helps in aggregation of data from different microservices
  • Support authentication responsibility for microservices
  • Can covert the protocol request from one type to other

Chain Of Responsibility Design Pattern

Let us take a look at this design pattern.

  • It is a design pattern where the output of 1 microservice acts as an input for other microservice
  • Uses synchronous HTTP request or response for messaging
  • The disadvantage of this pattern is that the response time for a single output can be much longer and the recommendation is not to make any longer chains

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Q4 What Do You Mean By Eureka In The Realm Of Microservices

Eureka is also known as the Netflix Service Discovery Server. This uses Spring Cloud and is most often known as the most used setup to start service discovery. It is also not that heavy on the application development process. This is the reason that it is quite popular among the developers of today.

Q18 Shed Light On Aop And Also Describe The Way In Which You Can Use It With Microservices

Microservices interview question and answers | Architecture design and Best practices

At the time of answering this question, you should always focus on the concerns of cross-cutting. The concerns of cross-cutting are the ways that extent numerous roads of a particular application. In this context, it is interesting to note that the concerns of cross-cutting usually fluctuate from the business logic of a particular application. This is the reason that the separation of concerns related to the cross-cutting nature is always a primary step that has to be taken in the application development process. AOP is also known as characteristic-oriented programming that goes a long way in making sure that business logic is applied correctly to enterprise-based applications.

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Question: What Is A Distributed Transaction In The Case Of Microservices

Answer: In the case of microservices architecture, it is possible that for a user request, the request could span multiple services. Transactions are handled by the transaction manager of each service using the common TraceID.

It is a best practice to include context as well as part of the request so that during investigation in case of any problems, the TraceID comes in handy to trace back the inter-services communication for the original user request and isolate the problem.

Jaeger is a tracing tool that can be used for end-to-end distributed tracing. Distributed transactions can be monitored to find dependencies between services, isolation of performance bottlenecks, and help in performance optimization.

Question: Why Are Containers A Good Infrastructure For Microservices

Answer: Containers are lightweight, easily packaged, and designed to run anywhere. Containers provide execution isolation at the operating system level. A single Operating system instance can support multiple containers with each container having its separate execution environment.

Containers are not mandatory as part of microservices architecture. For example, Netflix runs its microservices-based offerings on Amazon web services using AWS instance.

Fine-grained execution environments of containers and the ability of the container to accommodate co-located application components in the same operating system instance help greatly in achieving better server utilization rates. If any organization has the application of its microservices in the cloud environment, this will help in reducing the bills.

Container-based microservices applications can respond better to erratic workloads. Container initiation time is shorter, and this will help in user satisfaction.

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Database Or Shared Database Design Pattern

Let us take a look at this design pattern.

  • This design pattern talks about that either a microservice will have its separate database or two or more microservices can share a common database
  • Solve problems like:
  • Like data duplication and inconsistency
  • Different services having different storage needs
  • Data denormalization through shared databases per services

Q43 What Do You Know About Mike Cohns Test Pyramid

Microservices Architecture

Mike Cohn provided a model called Test Pyramid. This describes the kind of automated tests required for software development.

Fig 16: Mike Cohns Test Pyramid Microservices Interview Questions

As per pyramid, the number of tests at first layer should be highest. At service layer, the number of tests should be less than at the unit test level, but more than at the end-to-end level.

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What Are The Different Categories Of Design Patterns

The interviewer may ask this question to learn a bit more about your depth of knowledge regarding design patterns.

Example: “The three categories of design patterns are creational patterns, which allow freedom to choose how to create objects while hiding the logic structural patterns, which identify and simplify relationships between objects and use inheritance to give the objects additional functions and behavioral patterns, which identify how the objects communicate with one another.”

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What Is Semantic Monitoring

It combines monitoring of the entire application along with automated tests. The primary benefit of Semantic Monitoring is to find out the factors which are more profitable to your business.Semantic monitoring along with service layer monitoring approaches monitoring of microservices from a business point of view. Once an issue is detected, they allow faster isolation and bug triaging, thereby reducing the main time required to repair. It triages the service layer and transaction to figure out the transactions affected by availability or poor performance.

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Q16 What Do You Know About Spring Boot

Its a knows fact that spring has become more and more complex as new functionalities have been added. If you have to start a new spring project, then you have to add build path or add maven dependencies, configure application server, add spring configuration. So everything has to be done from scratch.

Spring Boot is the solution to this problem. Using spring boot you can avoid all the boilerplate code and configurations. So basically consider yourself as if youre baking a cake spring is like the ingredients that are required to make the cake and spring boot is the complete cake in your hand.

Fig 8: Factors of Spring Boot

What Are Restful Web Services

Microservices Interview Questions and Answers | Microservices Architecture Training | Edureka

Restful web services are web services that follow the REST architectural style. RESTful web services communicate with each other using CRUD operations. The REST architectural style emphasizes scalability and flexibility, which makes it compatible and frequently preferred for microservice architecture.

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Java Microservices Interview Questions On Inter

  • How does the Discovery Client work?
  • What do you understand about Zuul?
  • How does Load balancing work in Microservices?
  • What are the main features of Spring Boot?
  • What are the main features of the Axon framework?
  • Here are some Interview Questions on Java OOPS Concepts you should practice.

    These Java Microservices interview questions will help you prepare for your next Java developer interview.

    What Are The Different Strategies Used In Microservices Deployment

    Following strategies are used in Microservices deployment:

    • Multiple Service Instance per Host: It is used to run single or multiple service instances of the application on a single or multiple physical/virtual hosts.
    • Service Instance per Host: It is used to run a service instance per host.
    • Service Instance per Container: It is used to run each service instance in its respective container.
    • Serverless Deployment: It packages the service as a ZIP file and uploads it to the Lambda function. The Lambda function is a stateless service that automatically runs enough micro-services to handle all requests.

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    Q7 What Is The Difference Between Monolithic Soa And Microservices Architecture

    Fig 6: Comparison Between Monolithic SOA & Microservices Microservices Interview Questions

    • Monolithic Architecture is similar to a big container wherein all the software components of an application are assembled together and tightly packaged.
    • A Service-Oriented Architecture is a collection of services which communicate with each other. The communication can involve either simple data passing or it could involve two or more services coordinating some activity.
    • Microservice Architecture is an architectural style that structures an application as a collection of small autonomous services, modeled around a business domain.

    Q12 What Is Circuit Breaker Pattern In Microservices

    Top Microservices Interview Questions and Answers

    Circuit breaker is popular pattern for fault tolerance in microservices.


    Services sometimes call other services to handle requests. There is always a possibility that the other service is unavailable or taking longer time to respond. Precious resources such as threads might be consumed in the caller service while waiting for the other service to respond. This might lead to resource exhaustion, which would make the calling service unable to handle other requests. The failure of one service can potentially cascade to other services throughout the application.


    Thats where circuit breaker comes into play to prevent service failure from cascading to other services.

    Circuit Breaker

    Consider one service calling another service like an electric circuit breaker. When all works fine circuit breaker is closed.

  • When service detects that something is wrong with another service, the circuit breaks . When to break circuit?

  • return a fallback default response or serve previous responses from cache

  • After waiting for sleep window of x seconds , service attempts to call another service If request fails then circuit breaks . It repeats step 2 and 3 again. If gets a successful response back then circuit gets closed. Resume the requests again. All works fine.

  • Netflix Hystrix is one of the implementation of circuit breaker pattern.

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    Question: Which Acts As A Database Of Services In Microservices

    Answer: Service Registry is a database that contains the network locations of the service instance and helps in service discovery. It is critical that a service registry needs to be highly available and always up to date.

    Whenever any service starts, it needs to register itself with the Discovery Server. Netflix Eureka is a good example of a service registry.

    Some General Interview Questions For C# Design Patterns

    1. How much will you rate yourself in C# Design Patterns?

    When you attend an interview, Interviewer may ask you to rate yourself in a specific Technology like C# Design Patterns, So It’s depend on your knowledge and work experience in C# Design Patterns.

    2. What challenges did you face while working on C# Design Patterns?

    This question may be specific to your technology and completely depends on your past work experience. So you need to just explain the challenges you faced related toC# Design Patterns in your Project.

    3. What was your role in the last Project related to C# Design Patterns?

    It’s based on your role and responsibilities assigned to you and what functionality you implemented using C# Design Patterns in your project. This question is generallyasked in every interview.

    4. How much experience do you have in C# Design Patterns?

    Here you can tell about your overall work experience on C# Design Patterns.

    5. Have you done any C# Design Patterns Certification or Training?

    It depends on the candidate whether you have done any C# Design Patterns training or certification. Certifications or training are not essential but good to have.

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    What Is Bounded Context

    Bounded Context is a central pattern in Domain-Driven Design. In Bounded Context, everything related to the domain is visible within context internally but opaque to other bounded contexts. DDD deals with large models by dividing them into different Bounded Contexts and being explicit about their interrelationships.

    Monolithic Conceptual Model Problem

    A single conceptual model for the entire organization is very tricky to deal with. The only benefit of such a unified model is that integration is easy across the whole enterprise, but the drawbacks are many, for example:

  • At first, it’s very hard to build a single model that works for the entire organization.
  • It’s hard for others to understand it.
  • It’s very difficult to change such a shared model to accommodate the new business requirements. The impact of such a change will be widespread across team boundaries.
  • Any large enterprise needs a model that is either very large or abstract.
  • Meaning of a single word may be different in different departments of an organization, so it may be really difficult to come up with a single unified model. Such a model, even if created, will lead to a lot of confusion across the teams.
  • Can You Write A Java Program To Showcase The Left Triangle Star Pattern On The System Console

    Top 25 Microservice Interview Questions Answered – Java Brains

    This can be accomplished through nested loops and calculatingly adding spaces and stars as shown below:

    public class MindMajixPyramid            for                      System.out.println  // Go to next line after every row       }    }   public static void main}

    The output will be:

              *        * *      * * *    * * * *  * * * * *

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    How Does Docker Help In Microservice Architecture

    Docker helps in many ways for microservices architecture.

  • In a microservice architecture, there can be many different services written in different languages. So a developer might have to setup few services along with its dependency and platform requirements. This becomes difficult with the growing number of services in an ecosystem. However, this becomes very easy if these services run inside a Docker container.
  • Running services inside a container also give a similar setup across all the environments, i.e development, staging and production.
  • Docker also helps in scaling along with container orchestration.
  • Docker helps to upgrade the underlying language very easily. We can save many man-hours.
  • Docker helps to onboard the engineers fast.
  • Docker also helps to reduce the dependencies on IT Teams to set up and manage the different kind of environment required.
  • Question: What Are Microservices

    Answer: Microservices is a style of architecture wherein the key business capabilities of an application are exposed as loosely coupled services that can be independently deployed. Each service exposed is referred to as Microservice.

    For example, let us take the example of an eCommerce application. We can design and build separate microservices for key business functionalities of the eCommerce application like Authentication, Customer Account, Product Catalog, Product Ordering, Product Offering Qualification, Shopping Cart, Recommendation, Payment, Payment Method, Shipment Tracking, etc.

    Also Read: Microservice Architecture Everything you need to know about in 2021

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    Q5 What Are The Challenges In Microservices Based Application

    The challenges with microservices are as follows:-

  • Require good investment for infrastructure setup.
  • It is a nightmare to manage development, build, test, deployment and release cycles manually. DevOps is must to implement CI/CD automation.
  • Difficult to troubleshoot or debug an issue spanning across multiple microservices.
  • Overhead of inter communication between microservices
  • Challenges in development and testing where two or more microservices are involved.
  • Difficult to make configuration change across large fleet of microservices.
  • Operation and maintenance overhead.
  • Challenges comes with distributes system such as Network latency, fault tolerance, distributed transactions, unreliable networks, handling asynchronous operations.
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