Chapter 5. Migration and Integration

You never change things by fighting the existing reality. To change something, build a new model that makes the existing model obsolete.

R. Buckminster Fuller

One of the most pressing concerns that come bundled with every new technology stack is how to best integrate with existing systems. With the fundamental switch from monolithic to distributed applications, the integrity of a migration of existing code or functionality will have to be considered. The need to rearchitect and redesign existing systems to adopt the principles of the new world is undoubtedly the biggest challenge.

Migration Approaches

While Lagom and the reactive programing model is clearly favoring the greenfield approach, nothing is stopping you from striving for a brownfield migration. You have three different ways to get started with this.

Selective Improvements

The most risk-free approach is using selective improvements. After the initial assessment, you know exactly which parts of the existing application can take advantage of a microservices architecture. By scraping out those parts into one or more services and adding the necessary glue to the original application, you’re able to scale out the microservices. There are many advantages to this approach. While doing archaeology on the existing system, you’ll receive a very good overview of the parts that would make for ideal candidates. And while moving out individual services one at a time, the team has a fair chance ...

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