Kotlin Multimodule Android Architecture for Large-Scale Applications

As an Android application grows, a single Gradle module becomes harder to maintain. Build times increase, dependencies become tightly coupled, and unrelated features can accidentally depend on each other.

A multimodule architecture divides the application into independently managed modules while enforcing clear dependency boundaries.

Architecture

A large application can be organized like this:

app
├── core
│   ├── common
│   ├── network
│   ├── database
│   └── ui
├── domain
│   ├── auth
│   ├── orders
│   └── payments
└── feature
    ├── auth
    ├── profile
    ├── orders
    └── payments

Feature-Based Modules

Prefer business capabilities over extremely granular technical modules:

feature:auth
feature:orders
feature:profile
feature:payments

A feature can internally follow Clean Architecture:

feature:orders
├── presentation
├── domain
└── data

Gradle Configuration

Declare modules in settings.gradle.kts:

include(
    ":app",
    ":core:common",
    ":core:network",
    ":feature:auth",
    ":feature:orders"
)

A feature can consume shared functionality:

dependencies {
    implementation(project(":core:common"))
    implementation(project(":core:network"))
}

Prefer implementation over api unless a dependency must be exposed to consumers.

Dependency Direction

A healthy dependency graph might be:

app
 ↓
features
 ↓
domain
 ↓
core

Avoid direct feature-to-feature dependencies:

feature:orders → feature:profile

If two features need the same contract, move that contract to an appropriate shared module.

Dependency Inversion

Suppose orders needs user information. Define an abstraction:

interface UserProvider {
    suspend fun getUser(): User
}

The orders feature depends on the interface instead of the profile implementation.

Orders
   ↓
UserProvider
   ↑
Profile implementation

This keeps modules loosely coupled.

Core Modules

Useful shared modules include:

core:common
core:network
core:database
core:designsystem

Avoid creating one enormous core module containing every shared dependency. A giant core module eventually becomes another monolith.

Build Performance

Multimodule projects can improve incremental compilation because changes are isolated.

Measure:

• Kotlin compilation time
• Android compilation time
• Annotation/KSP processing
• Configuration time
• Dependency graph size

Too many poorly designed modules can increase build complexity, so module boundaries should represent meaningful ownership or architecture.

Testing

Each module can have independent tests:

feature:auth
├── unit tests
├── repository tests
└── UI tests

This makes it easier to validate features without always building the entire application.

Convention Plugins

Large repositories often repeat Gradle configuration. Convention plugins can centralize common settings such as Android, Kotlin, Compose, testing, and publishing configuration.

A module can then use:

plugins {
    id("company.android.feature")
}

instead of duplicating configuration everywhere.

Common Mistakes

Avoid:

• One giant core module
• Feature-to-feature dependency chains
• Excessive module creation
• Exposing dependencies unnecessarily with api
• Putting business logic into build configuration

Conclusion

Multimodule architecture is not about creating the maximum number of modules. It is about creating boundaries that allow teams to build, test, and change parts of an application independently.

For large Kotlin Android applications, combining feature modules, dependency inversion, focused core modules, and convention plugins provides a scalable foundation.

Useful Links

SDK Flutter: https://github.com/v-modal/vmodal_sdk_flutter

SDK Android: https://github.com/v-modal/vmodal_sdk_android

Discord: https://discord.gg/K72z28KUx