The Modular Monolith with Kotlin

--- title : " Modular Monolith in Kotlin: Enforcing Boundaries Without the Microservice Tax" published : true description : " Build a modular monolith in Kotlin with JPMS, internal visibility, and dependency inversion — compile-time isolation with a clear microservice extraction path." tags : kotlin, architecture, api, backend canonical_url : https://blog.mvpfactory.co/modular-monolith-kotlin-enforcing-boundaries --- ## What We Will Build Let me show you a pattern I use in every project that needs clean module boundaries but does not need the operational pain of microservices on day one. We will structure a Kotlin backend as a modular monolith using three enforcement layers: Kotlin's `internal` visibility modifier, JPMS `module-info.java` boundaries, and interface-driven contracts via dependency injection. By the end, you will have compile-time isolation between feature modules, shared ACID transactions, and a mechanical extraction path to microservices when your data actually demands