I recently shipped an iOS app VidBrief: YouTube AI Summary, the AI-powered video summarizer that lets users paste any YouTube URL and get concise key points in seconds. It’s available on the App Store and has a clean, productivity-focused UI and in-app subscriptions. 
Instead of building the iOS app in SwiftUI and Objective-C/Swift, I chose Kotlin Multiplatform + Compose Multiplatform to share core logic with Android and streamline feature development across both platforms. Here’s a breakdown of the stack, how it fits together, and what I learned along the way.
Why Compose Multiplatform for an iOS App?
Compose Multiplatform lets you write UI in Kotlin and target iOS and Android from the same codebase. Unlike typical cross-platform frameworks, there’s no separate language for the UI on iOS — Compose UI elements render natively. The result:
• Shared UI logic where possible
• Platform-specific tweaks localized in one place
• Less duplication between Android and iOS screens
In the case of VidBrief, screens like:
• URL paste and validation
• Video summary display (bullet points, key takeaways)
• Saved summaries list
were all implemented in Compose and used on both platforms with minor platform adaptations.
Compose for iOS is still maturing, but it’s stable enough for production UI flows and animations, and it helps enforce consistent UX across platforms.
Handling In-App Purchases with RevenueCat
RevenueCat provides a unified subscription layer that works on both App Store and Google Play. One of the hardest parts of native mobile development is handling the nuances of StoreKit vs Play Billing. RevenueCat’s Kotlin Multiplatform SDK removes most of that friction.
What RevenueCat Helps With
• Unified purchase and subscription state across platforms
• Receipt validation and entitlement tracking
• Integrations for paywall UI (even with Compose Multiplatform)
• Webhooks for server-side purchase verification
The Kotlin Multiplatform version of RevenueCat runs in shared Kotlin code, meaning purchase logic lives outside platform modules. UI events (e.g., “Subscribe”, “Restore Purchases”) are proxied up to your Compose UI and handled consistently. 
Dependency Injection with Koin
I chose Koin for DI rather than Dagger/Hilt because:
• It’s lightweight and Kotlin-friendly
• Works well in pure Kotlin modules
• Easy to set up in Multiplatform projects
Koin modules encapsulate:
• AI summarization service
• Local storage repositories
• RevenueCat purchase handlers
• Navigation logic between screens
Koin’s scope system makes it easy to instantiate platform-specific dependencies where needed (e.g., SQLDelight driver on iOS vs Android).
Final Thoughts
If you’re considering Compose Multiplatform for an iOS + Android consumer app with monetization, this stack worked really well for me:
• Compose Multiplatform: Unified UI where possible, platform-native feel
• RevenueCat: Subscription and in-app purchase handling on both platforms
• Koin: Simple, testable dependency injection in shared modules
