--- title: "React Native Performance Optimization" description: "Profile JS and native layers, fix startup, memory, and dropped-frame issues, and prove every performance gain with measurement." url: https://www.callstack.com/services/react-native-performance-optimization updated: 2026-11-09T16:02:38.628Z --- # React Native Performance Optimization Profile JS and native layers, fix startup, memory, and dropped-frame issues, and prove every performance gain with measurement. _[Expert Engineering](/ai-native-engineering) › [Architecture & Performance](/capabilities/architecture-performance)_ **Make your app feel fast again** Slow startups and janky scrolls cost you users. We profile JS and native layers, find the real bottlenecks, and fix them, no rewrite. Expensify shipped 3x faster startup with us. Measured before and after. ## Architecture & Performance - React Foundation Founding Member · 300+ commits to React Native · Contributing since 2016 - Industry runs on our tooling · 50M+ OSS downloads / month - 5x Faster message sending time - -28% CPU usage in critical trading flows - “Our app has hundreds of features and before we switched to Re.Pack we were struggling to scale the performance. Re.Pack is built on Webpack, so it allowed us to leverage existing tooling and approaches to scale more linearly. If the default tooling isn't working for your use case, I'd recommend giving Re.Pack a try!” — Mike Duminy, Principal Engineer / Klarna - 100+ Enterprise projects delivered ## What you get: Measure and fix the bottlenecks users feel. - **Root-cause profiling** We measure startup, TTI, thread load, and memory across JS and native to find what actually slows your app down. - **Fixes users feel** Smoother scrolling, faster screens, fewer dropped frames. We tune render paths instead of rewriting features. - **Smaller bundles** Tree-shaking and code splitting cut parse and load time. We took Dream11 from 50MB to 11MB, a 78% drop. - **Fewer re-renders** We kill wasteful renders and unbatched state updates. Questrade saw 33% fewer re-renders after our pass. - **Regression guardrails** Reassure and Rozenite benchmark performance in your CI, so a future commit can't quietly undo the gains. - **Low-end device wins** We optimize for the phones most teams ignore, where slow code hurts retention the most. **Fast apps keep users** Send us the slow flows. We'll find the root causes and tell you what's worth fixing, with numbers, not guesses. [Get a performance review](/contact) ## How we work together: Turn technical limits into shipped fixes. ### 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. - [26% Shorter Release Cycles for a Mobile Banking App](/case-studies/shorter-mobile-banking-release-cycles): 26% less time preparing releases - [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 - [Building an Agentic SDLC for a Web Launch in Under One Month](/case-studies/building-an-agentic-sdlc-for-a-web-launch-in-under-one-month): 3x estimated delivery acceleration - [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 **Fast apps keep users** Send us the slow flows. We'll find the root causes and tell you what's worth fixing, with numbers, not guesses. [Get a performance review](/contact) > Their ability to deliver, and follow through, is unparalleled in the React Native ecosystem. > > — Matt Hargett, Principal Software Engineer / Roblox We’ll connect you with the right expert within 24 hours. ## Let’s find the right path for your product. Still have questions? Whether you’re planning new work or unblocking an existing product, we’ll help you choose the right path forward. **How do I know if my React Native app has performance issues?** Performance problems aren't always obvious in development. If you see slow startup, janky scrolling, dropped frames, high memory use, or weak retention, your app likely needs optimization. We profile across JS and native layers to find the real bottlenecks and validate them with data. **Do I need to rewrite parts of the app to improve performance?** No. Most gains come from tuning render paths, bundling, and resource handling, not rewriting features. We focus on targeted fixes that deliver results without disrupting your existing work. **What's included in a performance review?** We measure startup, Time to Interactive, thread load, and memory across JS and native to find what actually slows your app down. You get the root causes and a clear view of what's worth fixing, with numbers, not guesses. **Can you help us implement the fixes too?** Yes. Our engineers apply fixes directly or work with your team to ship them safely. We tune render paths and cut wasteful re-renders so users feel the difference. **Will this affect our release cycle or CI/CD pipeline?** No. We work alongside your existing release process and add regression guardrails with Reassure and Rozenite, so a future commit can't quietly undo the gains. **What kind of results should we expect?** Teams typically see faster startup, smoother UI, and fewer dropped frames. Expensify shipped 3x faster startup with us. Every improvement is measured before and after, so you can see the gain. **Can you reduce our bundle size?** Yes. We use tree-shaking and code splitting to cut parse and load time. We took Dream11 from 50MB to 11MB, a 78% drop. **Can you optimize for low-end devices?** Yes. We optimize for the phones most teams ignore, where slow code hurts retention the most. Those users often feel the gains first. ## Open source - [Reassure](https://github.com/callstack/reassure): Performance testing companion for React and React Native - [React Native Harness](https://github.com/callstackincubator/react-native-harness): Harness brings Jest-style tests to real native environments so you can test TurboModules like you would test your React Native app: with JavaScript. - [Rozenite](https://github.com/callstackincubator/rozenite): Plug-and-play panels for React Native DevTools. Install, enable, and start debugging in minutes. - [Re.Pack](https://re-pack.dev/): A webpack-based toolkit to build your React Native application with full support of webpack ecosystem - [React Native Sandbox](https://github.com/callstackincubator/react-native-sandbox): Run multiple, isolated React Native instances within a single application