--- title: "Migrations & Upgrades" description: "We move your product off legacy systems onto a stronger, more secure foundation. Expert engineers and AI-assisted workflows help you execute complex migrations faster and with confidence." url: https://www.callstack.com/capabilities/ai-assisted-migrations updated: 2026-11-06T10:07:58.283Z --- # Migrations & Upgrades We move your product off legacy systems onto a stronger, more secure foundation. Expert engineers and AI-assisted workflows help you execute complex migrations faster and with confidence. _[Expert Engineering](https://www.callstack.com/ai-native-engineering) › Migrations & Upgrades_ **Execute complex migrations fast and with confidence.** We move your product off legacy systems onto a stronger, more secure foundation. Expert engineers and AI-assisted workflows help you execute complex migrations faster and with confidence. [Book consultation](https://www.callstack.com/contact) [Explore services](#services) Trusted by 100+ Enterprise clients Expensify · Ticketmaster · DirecTV · MLS · PWC · Evernote · AutoZone · MoMo · Dream11 · Rainbow · Futurewei · RIMAC · Hello Fresh · Haaretz · ForaTravel · CelcomDigi · Teamworks · Boats · Questrade · Dialogue Why migrate with Callstack ## Put expert engineers in charge of your migration. We lead your migration from codebase assessment to rollout. Agents accelerate repetitive changes while our engineers handle architecture, compatibility, and native integrations. - **Move off legacy faster.** Replace architectures that slow delivery and make change harder. - **Choose the right migration path.** Rebuild or migrate incrementally, balancing speed, cost, and risk. - **Reduce migration risk.** AI-native workflows improve planning, validation, and execution without giving up engineering control. - **Build faster after migration.** A stronger foundation makes future delivery easier, faster, and cheaper. Services ## Move to the stack that fits next. ### Technology Migrations - [Migration to React Native](https://www.callstack.com/services/migration-to-react-native): Move iOS and Android apps off separate native codebases onto one cross-platform stack, with the same product shipping to both stores from one codebase. - [Migration to Self-Hosted Infrastructure](https://www.callstack.com/services/migration-to-self-hosted-infrastructure): Move builds, CI/CD, and delivery off hosted platforms onto hardware you own, with full control over cost, security, and operations. - [Migration to Modular Architecture](https://www.callstack.com/services/migration-to-modular-architecture): Break a monolithic app into independently deployed mini-apps that let engineering teams ship in parallel. - [Migration to Expo](https://www.callstack.com/services/migration-to-expo): Move to Expo's managed workflow and EAS infrastructure. Faster builds, simpler releases, and full access to the modern React Native ecosystem. - [Migration to Next.js](https://www.callstack.com/services/migration-to-nextjs): Move legacy React or SPA apps onto Next.js, adding server rendering, streaming, and edge delivery to the React stack. ### React Native Modernization - [Migration to New Architecture](https://www.callstack.com/services/new-architecture-migration): Move React Native apps to the New Architecture (Fabric, TurboModules, and JSI), unlocking faster UI and synchronous native calls. - [React Native Upgrades](https://www.callstack.com/services/react-native-upgrades): Upgrade to the latest React Native release, patching security vulnerabilities and bringing the app up to date with new features and supported libraries. - **UX Modernization**: Improve high-impact journeys without rewriting the whole app, using product data, staged rollout, and real-device validation. - [Tech Debt Reduction](https://www.callstack.com/services/scalability-engineering): Refactor legacy code, tightly coupled modules, and deprecated APIs that block upgrades, migrations, and major feature work. Migrations & Upgrades ## Plan your next migration or upgrade. Send us the current stack and where you want to land. We'll come back with the migration path and the timeline. [Get my migration plan](https://www.callstack.com/contact) How we work together ## Move from migration plan to rollout. ### Extend your team 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 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 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 - 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](https://www.callstack.com/case-studies/modernizing-mobile-apps-in-production-with-react-native-and-self-hosted-ota) - [60 → 10min Faster builds after replacing Jenkins with EAS](https://www.callstack.com/case-studies/migrating-a-legacy-react-native-app-to-expo-for-faster-builds-and-simplified-releases) - [React Native Brownfield · Tooling for introducing React Native into existing native apps incrementally.](https://github.com/callstack/react-native-brownfield) - 100+ Enterprise projects delivered Case studies ## What shipping at AI speed looks like ### [Migrating From Native to React Native Without Slowing Down Delivery](https://www.callstack.com/case-studies/migrating-ios-and-android-apps-to-react-native-for-autozone) Expert Engineering · Automotive **2x** growth in mobile user base during the migration period ### [Migrating Questrade Edge Mobile to a Faster, More Scalable Architecture](https://www.callstack.com/case-studies/migrating-questrade-edge-mobile-to-a-faster-more-scalable-architecture) Expert Engineering · Finance **33%** fewer re-renders across most features ### [Migrating a legacy React Native app to Expo](https://www.callstack.com/case-studies/migrating-a-legacy-react-native-app-to-expo-for-faster-builds-and-simplified-releases) Expert Engineering · Retail & E-commerce **6x** faster builds after replacing Jenkins with EAS ### [Training HelloFresh engineers to build production apps with React Native](https://www.callstack.com/case-studies/training-hellofresh-engineers-to-build-production-apps-with-react-native) Expert Engineering · Retail & E-commerce **2.8x** increase in knowledge over 8 weeks (25% → 71% assessment scores) ### [A brownfield architecture that kept feature delivery moving across financial apps used by millions](https://www.callstack.com/case-studies/modernizing-mobile-apps-in-production-with-react-native-and-self-hosted-ota) Expert Engineering · Finance **4x** increase in RN pages across the tracked page set ### [Modernizing React Native codebase and adding platform features](https://www.callstack.com/case-studies/modernizing-react-native-codebase-for-7cup) Expert Engineering · Healthcare **130%** increase in users post-upgrade 10 years of React Native → Now in your AI stack ## Plan your next migration or upgrade. Send us the current stack and where you want to land. We'll come back with the migration path and the timeline. [Get my migration plan](https://www.callstack.com/contact) Open Source ## Build with our open-source tools. We open-source the tools behind our delivery model. Use them, fork them, or let us run them for you. [Check All Tools](https://www.callstack.com/open-source) [Explore AI Infrastructure](https://www.callstack.com/capabilities/self-hosted-ci-cd-infrastructure) - [React Native Brownfield](https://github.com/callstack/react-native-brownfield): Incrementally move your iOS and Android apps to React Native without breaking (552 stars) - [Agent Skills](https://github.com/callstackincubator/agent-skills): Callstack’s best practices on React Native performance optimization, upgrading, CI workflows, and brownfield migrations (1.7K stars) - [React Native Community CLI](https://github.com/react-native-community/cli): Command line tools to help you build React Native apps (13.5M downloads/mo) - [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 (1.4M downloads/mo) - [Rock](https://www.rockjs.dev/): Modular toolkit for teams building React Native apps (700 stars) - [Re.Pack](https://re-pack.dev/): A webpack-based toolkit to build your React Native application with full support of webpack ecosystem (2.2M downloads/mo) - [Reassure](https://github.com/callstack/reassure): Performance testing companion for React and React Native (1.5K stars) Insights ## Worth your time, by engineers. [Explore Insights](https://www.callstack.com/insights) - [React Native Brownfield Deep Dive: How RN Moves Into Native Applications](https://www.callstack.com/events/react-native-brownfield-deep-dive-how-rn-moves-into-native-applications) (Oct 9 · Talk): Artur Morys-Magiera will explain how React Native can move into an existing native app without forcing a big-bang rewrite. - [Same Destination, Different Roads: Migrating a Live App at Scale](https://www.callstack.com/events/same-destination-different-roads-migrating-a-live-app-at-scale) (Oct 8 · Talk): Łukasz Chludziński compares Greenfield and Brownfield approaches to migrating a live app, weighing continuity, delivery speed, cost, and risk. - [React Native in .NET MAUI: A Practical Brownfield Integration Guide](https://www.callstack.com/blog/react-native-in-net-maui-a-practical-brownfield-integration-guide) (Aug 27 · Article): This article walks through how we embedded React Native inside a .NET MAUI application using a brownfield setup. It covers the packaging layer, lifecycle wiring on iOS and Android, navigation through MAUI Shell, and shared state between the MAUI and React Native runtimes. - [Adoption of Brownfield in React Native](https://www.callstack.com/events/adoption-of-brownfield-in-react-native) (Aug 27 · Talk): Artur Morys-Magiera will explain how teams can adopt React Native incrementally inside existing native applications. - [Agentic AI in the Wild - Boston Dev Community Meetup](https://www.callstack.com/events/agentic-ai-in-the-wild---boston-dev-community-meetup) (Aug 18 · Meetup): Join us in Boston on August 18 for an evening focused on a question most teams hit quickly with AI agents: how do you make them dependable once they leave the prototype phase and start touching code, workflows, and delivery timelines? - [Migration to React Native in 2026 Starts With a Delivery Question](https://www.callstack.com/blog/migration-to-react-native-in-2026-starts-with-a-delivery-question) (Aug 3 · Article): This article helps mobile teams choose between brownfield and greenfield React Native migration. It explains how each approach shifts risk across continuity, native dependencies, delivery pressure, verification, and architecture ownership, and introduces a checkpoint-based path for teams that want to test a greenfield rebuild before committing. It also shows where AI can help and what still needs human control. - [How we made Hybrid iOS apps compile 39% faster with React Native Brownfield](https://www.callstack.com/blog/how-we-made-hybrid-ios-apps-compile-39-faster-with-react-native-brownfield) (Jul 8 · Article): React Native Brownfield 3.10 brings iOS prebuilts into the packaging flow, removing a major compile step from hybrid app builds. This article explains how the integration works, what changed under the hood, and what our benchmark results show for React Native and Expo projects. - [AI-Assisted React Native Migration for TV: Lessons From Zattoo](https://www.callstack.com/blog/ai-assisted-react-native-migration-for-tv-lessons-from-zattoo) (Jun 11 · Article): Zattoo started its React Native TV migration before today’s AI-assisted workflows became common. Their story shows where AI can now support similar migrations, from onboarding and refactoring to testing and platform-specific implementation work.