Decomposing a Monolith: Strategies

Many successful software systems begin as monolithic applications. A monolith is an application where multiple business capabilities are implemented and deployed together as a single unit. For example, an e-commerce application might contain product management, inventory, ordering, payments, and shipping within one codebase.

This is not necessarily a bad design. Monoliths are often easier to develop, test, deploy, and debug, especially when the application and engineering team are small.

However, as the system grows, a monolith can become difficult to maintain. A small change to payment processing might require rebuilding and deploying the entire application. Multiple teams might struggle with the same codebase, and scaling one resource-intensive component could require scaling everything.

At this point, organizations may consider moving toward microservices. But decomposing a monolith is not simply about moving code into separate applications.

The real challenge is identifying meaningful service boundaries, separating data ownership, and migrating functionality without disrupting the business.

In this chapter, we'll explore practical strategies for decomposing a monolith, and the trade-offs involved.