Modernizing Legacy Systems: A Domain-Driven Approach to Microservices
From what I’ve seen in the clients, the real headache comes when you refactor the old system to fit the new technology architecture. Teams started to get coupled with each other more than before. This complicates the development process with increasing inter-team dependencies and makes maintenance work challenging with the same business value.
Shifting gears to a microservices setup isn’t just about technical competency; it’s really about making something valuable out of it. To ensure effective decomposition of legacy services, it is essential to follow Domain-Driven Design (DDD) principles and incorporate them into the design rules.
Let’s discuss how DDD iteratively approaches. Understanding this is key. We start by discovering the key events on a system and extend these events with process modeling, which navigates us to decompose the system into bounded contexts. Designing inbound-outbound communication in the bounded context and discovering ubiquitous language is a good logical practice that guides you to make the right segregation. Next, you need to figure out the aggregates in the bounded context to efficiently operate processes within the context by covering functional and non-functional requirements. At this step, teams return to events, process design, or bounded context definitions until they refine enough to design aggregates.
Figuring out the right size for the needed services (be it micro, mini, or macro) depends a lot on how well you define Bounded Contexts and the aggregates. Decomposition must ensure that different bounded contexts are separated as different microservices. If this separation is not clear, it is the right time to iterate one more time, starting from events and the bounded context definitions.
Another important principle during microservice decomposition is that an aggregate should be managed by a single microservice. However, a single microservice may manage several highly cohesive aggregates. This approach ensures a clear, manageable boundary within each microservice, promoting service cohesion and focus.
As I mentioned earlier, non-functional requirements are vital constraints. Do not forget about the behind-the-scenes stuff, like how much data can move through or whether you need high computing requirements. The new design should ensure components can scale up or keep running when things get rough. Decomposition should consider non-functional requirements like scalability and resilience, ensuring that the architecture meets current functional needs and is robust and adaptable for future demands.
In conclusion, applying DDD principles and carefully considering the decomposition process in a microservices architecture is not just a technical ambition. It’s a strategic approach that aligns closely with business objectives, ensuring that technological improvements contribute directly to creating business value. This mindset shift from technology-centric to value-driven development is essential for modern software engineering practices.
