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  /  Latest News   /  Step-by-step migration guide to microservices

Step-by-step migration guide to microservices

In this article we’ll give you a full step-by-step roadmap on how to migrate from monolith to microservices.


Once you’ve decided which parts and in which order to extract, now’s the time to pick up the first candidate in your queue. You need to define the refactoring strategy, design the microservice, estimate the efforts, and plan the iteration. It’s also important to remember that the new approach would require certain changes in your Continuous Integration/Continuous Delivery (CI/CD) and testing procedures. So, it makes sense to agree on those changes with your team and adjust your processes properly.


First step: Choose the strategy


Your next step will be to select the correct refactoring strategy to migrate the chosen functionality into an independent microservice. There are two proven strategies:



  • Isolating features inside the monolith with subsequent separation into a microservice



This strategy implies the smooth removal of connections with other functionality while keeping the candidate inside the monolith until it’s ready for separation. Once all the connections are removed and the new API is designed, the candidate is separated from the monolith and deployed as a separate microservice.



  • Too many connections with other features;
  • Active development and a lot of changes inside the monolith that affect the candidate.


  • Copying the functionality and turning it into the microservice



This means creating an independent copy that is further developed into the microservice. The initial feature list still remains operational inside the monolith. Once its integrations are fully implemented and tested, the initial functionality can be deleted.



  • Need to have more flexibility in the microservice engineering process;
  • Low probability of changes to the candidate while the microservice is being implemented.


Both those approaches have proven their efficiency. However, they also have one common bottleneck. Once the migration process is done in parallel with active development, new dependencies may emerge between while the new microservice is being implemented.


In this case, you would need to track and resolve those through new API endpoints or via shared libraries with common parts of a code. And on each occasion, this would take more time and effort than if the functionality was still a single whole with the entire monolith.


Second step: Design architecture and changes to CI/CD and test processes


First off, you need to design the future microservice and specify changes that should be brought to your CI/CD and testing processes. That is a crucial step that forms the baseline for a further successful conversion.


This is what you need to do:

  • Define the exact code in your application that will be attributed to the microservice;
  • Design API interfaces through which it will cooperate with the monolith and other microservices;
  • Choose a stack of technologies that will be used for the introduction of communication with microservice.


The new microservice will require a corresponding CI/CD. That is why your existing process may require significant changes. In case you did not use them before, it may be the right time to introduce those as they are crucial for any considerable refactoring of existing code. It helps automate and accelerate all phases from coding up to deployment as well as reduce error detection time.


You also should keep in mind that with this migration, you’ll also need to make some changes to your testing strategy. When a microservice is launched, testers should bear in mind that now they can communicate directly with each component. The test team would need to look for issues at the levels of microservices interactions and infrastructure as well as at the overall app level.


Each of these levels requires its own resources and set of testing tools. Test automation can help in this case. With the proper testing strategy, your team can seamlessly transit to microservices at the optimal time and without significant troubles.


Third step: Set up CI/CD


You can start changing Continuous Integration/Continuous Delivery simultaneously with the main development. Or even before, so that you can successfully maintain microservice during its development and after it’s launched.


  • CI allows you to easily integrate your code into a shared repository.
  • CD allows you to take the code stored in the repository and continually deliver it to production.


There’s an even more effective way. CI can transform code from a repository to a compiled package (ready to be deployed) and store it in Artifactory. CD can deploy compiled packages from Artifactory to the destination environment. In this scenario, CI/CD processes are independent of each other, don’t have intersection steps, and could be changed and/or improved separately from each other.


Fourth step: Implementation and testing


This is the final step. Now it’s time to implement everything that has been planned. At this point, the dev team encapsulates the features into an independent microservice, cuts off the closely linked connections with the parent app, and implements the API gateway that becomes a single point through which it can communicate with the parent program and other microservices.


Meticulous testing should be an integral part as you need to ensure that the microservice works exactly as expected. You also need to be sure that all possible errors or issues are tackled before the new environment is launched. Test coverage development can start in sync with the implementation (or in advance) to monitor the results as soon as possible. Testing is completed when the microservice operates perfectly in the new environment.


The final result of this stage is a fully functional microservice that operates in isolation from the monolithic architecture. With proper and careful planning, the deployment is completed as forecasted and does not create any delays or hindrances in the overall development process.