Android Engineering Strategy for Global App Launch

Karthi from Mercari's Android team reveals why they ditched cross-platform frameworks for their global marketplace launch. The decision wasn't about native vs. hybrid ideology, it was about leveraging 10M+ downloads worth of battle-tested infrastructure.

Mercari built a new global e-commerce app serving multiple countries with a small team and aggressive timeline. Despite having Flutter and React Native experience across their product portfolio, they chose native Android with Jetpack Compose by making strategic bets on reusability over theoretical speed.

Key Takeaways

• Single global build serves all countries via BFF layer and remote config
• Monorepo with enforced boundaries using modules-graph-assert prevents dependency sprawl
• Switched from REST to gRPC with Wire for performance and type safety
• Reused proven architecture from Japan app (10M+ downloads) instead of rebuilding
• BFF layer enables country-specific experiences without separate builds

The article details their specific monorepo structure rules and explains the hidden complexity costs they avoided from their Flutter experience.