High-Performance React Native App Development & Optimization

If your mobile app is slow, your users are too. In a world where every tap and swipe is compared to the smoothest apps on a user's phone, performance isn't just nice to have—it's necessary to protect your income. BYBOWU makes and tunes React Native and Expo apps that feel instant, scroll smoothly, and work well in the real world.

We are a US-based team that works on making React Native apps better and Expo apps that work really well in 2025. We look for bottlenecks and get rid of them without slowing down the product, from cold start improvements to memory management and frame consistency. You will see real improvements on real devices, not just wins in the lab.

Do you want to see how optimization fits into your plan? Look through our wider services or look into the results in our portfolio.

Metrics for Performance

We make the numbers that really show how happy and likely users are to stay with us better. No metrics for vanity, only signals that show how responsive and stable something is.

• Cold and warm start time: Time to first screen and time to interactive after splash. Targets based on the type of device, like <2s on mid-range Android.
• Frame rate and jank: FPS stays stable at 60 with few JS and UI thread frame drops; scrolling works well in lists and charts.
• Responsiveness to input: the time it takes for a tap to render, a gesture to respond, and a navigation transition.
• Size of the bundle and code split coverage: A smaller initial JS lowers the cost of starting up and the amount of memory it uses.
• Memory usage and leaks: Memory that stays the same, the health of the image cache, and cleanup when you move around.
• Crash rate and ANR: Sentry/Crashlytics keeps things stable when there is real traffic, and Android has ANR mitigation.

What tools we use: Flipper performance plugins, Hermes profiling, Xcode Instruments (Time Profiler, Allocations), Android Studio Profiler, React DevTools, Expo's EAS performance traces, and real-device "bench routes" to test core screens before and after each change.

Ways to Optimize

A lot of small, right choices lead to high performance. We adjust the rendering, data flow, network, and runtime to get rid of stutter and lag while still keeping the codebase easy to work with.

Rendering and Navigation

1. Hermes is the default option because it starts up faster and uses less memory. We start Hermes, check bytecode caching, and keep track of how long it takes to compile and parse.
2. Fabric/TurboModules readiness: If you want to cut down on bridge burden and minimize the amount of JS-to-native chatter per frame, switch to the new design.
3. Changes to React Navigation: While you can, utilize native-stack, disable on react-native-screens, and avoid using heavy renders in navigators.
4. Use useCallback and useMemo to keep props stable, don't re-render context that doesn't need to be across big trees, and memoize expensive subtrees.
5. Code splitting: dynamic import for flows that aren't used very often (like settings and legal screens) to make the first bundle smaller.

List Virtualization and UI Density

• FlatList tuning: use getItemLayout for fixed heights, removeClippedSubviews where it makes sense, balance windowSize and batch size, keep keyExtractor stable, and don't use inline renderItem functions.
• Skeletons and placeholders: Lightweight skeleton states make perception smoother; hold off on heavy payloads until after the first paint.
• Don't use nested scrollable lists or too many shadows and blurs. Instead, use lightweight design patterns that look good and are cheap to render.

Networking, Caching, and State

• HTTP performance: Use keep-alive, compression, and CDN edge caching for APIs that can use them. On Wi-Fi, prefetch important endpoints.
• TanStack Query (React Query) or SWR can be used for request deduplication, background refetching, and normalizing network use.
• Storage on the device: Don't overload AsyncStorage; instead, use react-native-mmkv for quick, memory-mapped key/value.
• Updates that are hopeful and sync in the background: While the data settles, keep the UI responsive and roll back if something goes wrong.
• Offline-first flows: Cache lists and assets with set TTLs; work well on bad networks.

Images, Media, and Asset Strategy

• Set the right size for images: Use Expo Image or FastImage for caching and resize at the server or build time with sources that are aware of device density.
• Load assets below the fold slowly and media above the fold quickly during splash or navigation transitions.
• SVG vs. bitmap: Use SVG for icons; change big PNGs to smaller ones; compress them a lot without losing quality.

Cost of Starting Up and Running

• Put off work that isn't urgent: Use InteractionManager to move analytics, feature fetches, and optional modules to times when they aren't being used.
• Reduce polyfills and global side effects: Only tree-shake and conditionally import packages when you need to.
• Flags for building production: Turn on minification, turn off dev menus and logging, and send symbol maps for crash triage without making the runtime bigger.

Memory Management

• Cleanups: To avoid leaks, make sure that event listeners, timers, and subscriptions are all unsubscribed when the component is unmounted.
• Managing the image cache: Limit the size of the cache and clear it when you get low-memory signals. Don't decode huge images into memory.
• Teardown: When moving away from heavy screens (like cameras, maps, and charts), release big modules.
• Don't allocate memory for each frame: Don't make new objects in render loops; instead, precompute styles and arrays.

Gestures and Animations

• Reanimated and Gesture Handler: Move animations to the UI thread and don't use RunOnJS in per-frame loops.
• Microinteractions: Use light transitions and motion curves that feel quick without putting too much stress on the GPU.
• Charts and canvases: When datasets are big, use native-backed chart libraries or canvas-based rendering.

Expo and EAS

• Updates to the Expo SDK: Stay up to date on fixes for Hermes, performance, and memory. Check that your EAS Build profiles are optimized.
• DevClient for real profiling: Use production flags to test locally and find real bottlenecks.
• Selective prebuild or bare migration: When you need custom native modules to improve performance, we plan a safe, step-by-step path.

Observability and Guardrails

• Crash and performance logging: Sentry/Crashlytics with custom breadcrumbs and performance spans.
• Alerts for runtime: Keep an eye on JS thread stalls, long tasks, and ANR, and send alerts when they go over certain limits.
• Release hygiene: Use feature flags, staged rollouts, and rollback plans to make sure that performance changes are safe to ship.

Case Studies

Ecommerce App: Faster PDP, More Conversions

A retail customer had trouble with stuttering on product detail screens. We adjusted the FlatList variants, made the hero images smaller, and moved to Hermes. The result: 40% fewer dropped frames, startup 28% faster, and checkout conversion rate up by 8%, all without redesigning.

Field Service: Stable Even When Connections Are Weak

Field technicians needed networks that worked consistently. We used react-query, background sync, and MMKV storage to cache queries. The app was much more responsive; task completion times dropped 22% and sync errors dropped 63%.

Fintech: Startup Time, Slashed

A fintech app had trouble with big bundles and analytics that happened at the same time. We used InteractionManager, split code by route, and put off tasks that weren't important. On mid-range Android, the cold start time went from 3.7 seconds to 1.9 seconds, and the crash rates went down after fixing memory spikes during login.

Want more examples? Check out our portfolio.

Questions and Answers

What can I do to make my app run better?

Begin with the biggest victories: Use code splitting to make the bundle smaller, tune FlatList, move animations to the UI thread with Reanimated, and compress and cache images. Keep an eye on memory and remove listeners and objects when the screen changes. We'll make a plan just for your app and its users.

Is Expo quick enough for production apps?

Yes. The latest Expo SDK, Hermes, and EAS Build can make Expo apps very fast. For performance-heavy features, we prebuild native modules or move parts to bare workflow as needed.

How do you measure success?

We set thresholds for each device tier and monitor startup time, FPS, responsiveness, memory stability, and crash rates. We also track retention, conversion, and ratings to link engineering improvements to business impact.

Will improvements make the app bigger?

Usually not. We reduce app size by pruning dependencies, splitting code, and optimizing assets. If adding a native module increases size, we weigh the tradeoffs.

Do you know how to move Fabric/TurboModules?

Yes. We check library readiness, plan phased rollouts, and test features behind flags. This reduces bridge overhead and improves smoothness on animation-heavy screens.

What devices do you test on?

We test on iOS and Android, including mid-range Android devices where performance problems often show up first. Real-device testing plus profiling tools ensure changes hold up in production.

Deliverables and Engagement

• Profile startup, navigation, lists, and memory; find quickest ways to stable FPS and responsiveness.
• Implementation sprints with feature flags and staged rollouts.
• Reporting: metrics, videos, and prioritized backlog.
• Guardrails: Flipper dashboards, alerts, and performance budgets.

Need to balance scope and budget with your timeline? We’ll prioritize high ROI fixes first. Learn more on our services page.

Get in Touch

Ready to ship a React Native app that feels fast and reliable? We’ll make a list of changes users—and KPIs—can feel, and then deliver them.

• Email: [email protected]
• Tell us your stack (Expo or bare), your top problem screens, and your target devices. We’ll provide a plan in 48 hours.
• Prefer a short intro? Reach out via our contact form.