Nucleus, the backend behind this portfolio, is a useful real example for comparing deployment boundaries. It contains Blog, Course, Project, Finance, and other modules inside one Laravel application. The public Next.js website and mobile companion are separate clients, while Nucleus owns persistence and content rules.

This walkthrough uses that existing modular monolith to examine what a service extraction would change. The extraction example is a design exercise, not a claim that Nucleus's invoice or notification modules have already become independently deployed services. No performance improvement or traffic capacity is assumed.

Folders organize code; deployment and ownership define the boundary

A monolith is deployed as one backend application. It can still have well-defined modules, dependency rules, queues, and multiple web or worker processes. In Nucleus, ModulesServiceProvider discovers module routes, migrations, and commands within the same application.…