First, just to repeat, you don't need to modularise your app to use jlink. You modularise to enjoy additional security and evolution benefits. > How easy is it

First, just to repeat, you don't need to modularise your app to use jlink. You modularise to enjoy additional security and evolution benefits. > How easy is it for the average greenfield enterprise to start as a modular app? As easy as a non-modularised one. > How easy is it for the average brownfield enterprise app started 10 years ago to convert to a modular app? This one is harder to answer because you can only modularise (i.e. encapsulate in modules) code that is actually modular (cleanly separates API and implementation into different packages, no circular dependencies among components that are to become modules etc.). So it depends on how modular your codebase already is. In many situations it could require a not-insignificant refactoring, and so worth it if you really want the best security and encapsulation (which was the case for the JDK itself, which is now fully modularised). In other situations it could make sense to leave things alone and only modularise new project components (modules and code outside modules can mix). Either way, modular or not, using link to produce a custom runtime is a good idea!