--- title: "Migration to Modular Architecture" description: "Break a monolithic app into independently deployed mini-apps, so teams build and ship in parallel without blocking each other." url: https://www.callstack.com/services/migration-to-modular-architecture updated: 2026-11-09T15:59:52.840Z --- # Migration to Modular Architecture Break a monolithic app into independently deployed mini-apps, so teams build and ship in parallel without blocking each other. _[Expert Engineering](/ai-native-engineering) › [Migrations & Upgrades](/capabilities/ai-assisted-migrations)_ **From one monolith to parallel teams** Past a certain team size, the codebase becomes the bottleneck. We split monolithic apps into independently built and deployed mini-apps - using Re.Pack and Module Federation, which we maintain - so teams ship on their own schedule. ## Migrations & Upgrades - React Foundation Founding Member · 300+ commits to React Native · Contributing since 2016 - Industry runs on our tooling · 50M+ OSS downloads / month - 4x More React Native pages · 30% React Native adoption - 60 → 10min Faster builds after replacing Jenkins with EAS - React Native Brownfield · Tooling for introducing React Native into existing native apps incrementally. - 100+ Enterprise projects delivered ## What you get: Modularity without the rewrite. - **Architecture blueprint** Module boundaries drawn along team and domain lines, with explicit dependency contracts. - **Re.Pack and Module Federation** Runtime loading of independently deployed bundles, on tooling we maintain in open source. - **Incremental extraction** Modules leave the monolith one at a time; the app ships throughout. - **Shared foundation strategy** One approach to design system, state, and native modules across all mini-apps. - **Independent release trains** Each team deploys its module without waiting for a monorepo release. - **Governance model** Ownership, versioning, and compatibility rules that keep modularity from becoming fragmentation. ## How we work together: Move from migration plan to rollout. ### Extend your team (1 week) Our senior engineers join your team to ship features, guide technical decisions, and strengthen delivery. - Your roadmap and workflow - Expertise shared as we work - Flexible timezone coverage ### Deliver a project (1-12 months) We take agreed work from technical planning to release, with clear responsibilities and progress you can see. - 3 Callstack engineers ship like 6 - Impact visible before sprint two - End-to-end delivery ### Solve specific challenge (as needed) We address a performance, migration, or infrastructure challenge, or run training around your team’s needs. - Focused reviews or implementation - Knowledge your team keeps - Outcomes guaranteed with contract ## What shipping at AI speed looks like. - [Modernizing a Crypto Trading Platform With React Native and Self-Hosted OTA](/case-studies/modernizing-mobile-apps-in-production-with-react-native-and-self-hosted-ota): 4x increase in RN pages across the tracked page set - [Migrating Questrade Edge Mobile to a Faster, More Scalable Architecture](/case-studies/migrating-questrade-edge-mobile-to-a-faster-more-scalable-architecture): 33% fewer re-renders across most features - [Migrating a Legacy React Native App to Expo for Faster Builds and Simplified Releases](/case-studies/migrating-a-legacy-react-native-app-to-expo-for-faster-builds-and-simplified-releases): 6x faster builds after replacing Jenkins with EAS - [Training HelloFresh Engineers to Build Production Apps With React Native](/case-studies/training-hellofresh-engineers-to-build-production-apps-with-react-native): 2.8x increase in knowledge over 8 weeks (25% → 71% assessment scores) **Ship in parallel, not in queue.** Incremental modularization that gives teams back their own release schedule. [Get my migration plan](/contact) > We had been struggling with React Native application performance until we met Callstack. > > — Huỳnh Chí Hùng, Associate Director, MOMO We’ll connect you with the right expert within 24 hours. ## Let’s find the right path for your product. **Is this micro-frontends for mobile?** The same idea, adapted to React Native's constraints: independently built bundles loaded at runtime into one host app, with shared dependencies managed deliberately. **Is runtime code loading allowed on the app stores?** JavaScript-level updates within platform policies are established practice. We design the update flow to stay inside Apple's and Google's rules. **What is the performance cost?** Managed well, minimal: shared dependencies load once, and bundles are cached. We benchmark startup and memory before and after each extraction. **How do teams share a design system?** As a versioned, federated dependency with compatibility rules, so upgrades roll out without forcing lockstep releases. **Can agents accelerate the extraction?** Yes. The repetitive parts - moving code, rewiring imports, updating tests - are exactly what our migration agents automate, with engineers owning the boundaries. **When is this overkill?** Below roughly two or three teams on one app, modularity costs more than it returns. We will tell you if a modular monolith is the better answer. ## Open source - [React Native Brownfield](https://github.com/callstack/react-native-brownfield): Incrementally move your iOS and Android apps to React Native without breaking - [Agent Skills](https://github.com/callstackincubator/agent-skills): Callstack’s best practices on React Native performance optimization, upgrading, CI workflows, and brownfield migrations - [React Native Community CLI](https://github.com/react-native-community/cli): Command line tools to help you build React Native apps - [React Native Builder Bob](https://github.com/callstack/react-native-builder-bob): Simple set of CLIs to scaffold and build React Native libraries for different targets - [Rock](https://www.rockjs.dev/): Modular toolkit for teams building React Native apps