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Learn Microservices with Spring Boot - Chapter 6

This repository contains the source code of the practical use case described in the book Learn Microservices with Spring Boot (2nd Edition).

The book follows a pragmatic approach to building a Microservice Architecture. You start with a small monolith and examine the pros and cons that come with a move to microservices.

Chapter 6 version

In Chapter 6, you enter into the world of microservices with a first approach that uses synchronous processing and orchestration from the Multiplication microservice. As the book explains, this approach has many issues: tight coupling, domain pollution, etc. Yet we covered it to learn why it's important to embrace Asynchronous Processing and Eventual Consistency in microservice architectures.

Logical View - Chapter 6

The main concepts included in this chapter are:

  • Monolith vs. Microservices: Pros and Cons
  • Starting with a Small Monolith
  • Non-Functional Requirements in Microservices
  • Building the Gamification microservice
  • Connecting microservices with synchronous interfaces
  • Analysis: Transactionality, Eventual Consistency, Fault Tolerance

As usual, you go through a practical implementation of a microservice architecture that evolves to show you the real problems, and the tools you can use to solve them.

The next figure shows the domain models after introducing the Gamification domain (in the new microservice):

Domain model

Check the Book's Web Page to see the complete list of chapters.

Running the app


  • JDK 14+
  • Node.js v13.10+
  • npm 6.13.7+
  1. To start the Multiplication microservice, you can use the command line with the included Maven wrapper:
    multiplication$ ./mvnw spring-boot:run
  2. To start the Gamification microservice, you do the same from its corresponding folder:
    gamification ./mvnw spring-boot:run
  3. The React application can be started with npm. First, you need to download the dependencies with:
    challenges-frontend$ npm install
  4. Then, you start the server with:
    challenges-frontend$ npm start

Once the backend and the fronted are started, you can navigate to http://localhost:3000 in your browser and start resolving multiplication challenges. This time, you'll see the Leaderboard.

Application - Screenshot


  • Do you have questions about how to make this application work?
  • Did you get the book and have questions about any concept explained within this chapter?
  • Have you found issues using updated dependencies?

Don't hesitate to create an issue in this repository and post your question/problem there.

About the book

Are you interested in building a microservice architecture from scratch? You'll face all the challenges of designing and implementing a distributed system one by one, and will be able to evaluate if it's the best choice for your project.

Visit for all the details about the book.


You can buy the book online from these stores:

Source code by chapter (all repositories are available on Github)

Extra chapters: