Staff Augmentation
Add React Native engineers to your team for a performance push, a native module, or a new feature release.
Where do React Native performance problems come from?
Every screen in a React Native app renders real native views on iOS and Android. JavaScript drives those views, and it runs next to the platform's own UI thread. That split explains almost every performance problem you'll see.
When the JavaScript side is busy, taps feel late. When the native side is overloaded, scrolling stutters. What follows is the briefing we'd give a new lead joining an app that's already live, covering where to look first and what to leave alone.
Which well known apps are built with React Native?
Meta uses React Native inside Facebook and Instagram. Microsoft uses it in parts of its Office apps. Shopify and Discord have both written publicly about building their mobile apps with it. These are the React Native examples people cite most, and they prove one thing. The framework can carry large, busy apps.
They don't prove your app will be fast by default. Each of those teams put real effort into profiling, native modules, and custom tooling. The framework made that work possible. It didn't make that work optional for anyone.
After a slow release, the usual advice is to wrap every component in memo and every handler in useCallback. It feels responsible. In practice it adds comparison work to every render, clutters the code, and rarely touches the real problem. On most apps, a handful of screens cause nearly all the visible jank. They're almost always long lists, heavy images, or animations driven from JavaScript.
Where memoization actually pays off
Fix those screens first. Memoize where a profiler shows a component rerendering for no reason, and leave the rest. Small, targeted fixes are easier to review and easier to keep.
Why do React Native apps drop frames?
React Native apps drop frames when one of two threads can't finish its work inside a frame. The JavaScript thread runs your React code, state updates, and business logic. The UI thread draws native views and handles gestures. If either runs long, the user sees a stutter, a late tap, or a frozen spinner.
The fix depends on which thread is struggling. So find that out before you touch any code. Open the performance monitor in the developer menu. It shows both frame rates side by side while you use the app as normal.
Measure in a release build every time. Debug builds run extra checks and load JavaScript differently, so they feel slower than what users get. Fixes tuned against them can mislead you. Make a mid range Android phone your main test device, because flagship phones hide problems that lots of real users will see.
Symptoms that point to each thread
You can usually trace a stutter to one thread just by how it looks. Use this list to form a first guess, then confirm it with the performance monitor.
- Taps respond late. Usually a busy JavaScript thread, often from heavy state updates or blocking work in a handler.
- Scrolling stutters while the screen looks idle. Usually the UI thread, often from large images, deep view trees, or shadows on many items.
- Animations freeze during data loads. Animations driven from JavaScript share its thread, so they stop whenever it's busy.
- Lists show blank areas during fast scrolls. The list can't render rows fast enough, which points to expensive row components.
- The first screen takes ages. Startup work, bundle size, and early network calls all compete before anything appears.
Do Hermes and the New Architecture make React Native faster?
They help, mostly at startup and where JavaScript meets native code. They won't fix slow screens alone. Hermes is the JavaScript engine Meta built for React Native. It compiles JavaScript to bytecode at build time, which usually shortens startup and lowers memory use compared with parsing source on the device.
The New Architecture swaps the old asynchronous bridge for a direct interface between JavaScript and native code. It also brings a new renderer and a new native module system. Calls that used to be queued and serialized can now happen directly, which removes a long standing source of delay in gesture heavy screens.
Both are the default in current React Native setups, yet older apps often still run without them. Check the build settings before you assume you have them. Expect some third party libraries to need updates during the move. And remember that a heavy list or an oversized image stays slow on any engine.
How does the Thread Time Audit rank performance fixes?
The Thread Time Audit is the five step routine we run on every React Native app we inherit. It usually takes days, not weeks. What you get is a short, ranked list of fixes, not a vague plan to "improve react native performance" someday.
- Record the slowest real journeys. Pick the three flows users touch most, such as opening the app, scrolling a feed, and checking out. Record each in a release build on a mid range Android phone with the performance monitor on screen.
- Name the thread for every stutter. For each drop, note whether the JavaScript frame rate, the UI frame rate, or both fell. This one step stops a team from spending a sprint on the wrong layer.
- Fix lists and images first. Use a virtualized list with stable keys, fixed row heights where you can, and light row components. Resize images on the server to their on screen size and use a caching image component.
- Move motion off the JavaScript thread. Turn on the native driver for Animated where the properties allow it, or use Reanimated, which runs animation logic on the UI thread. Put gestures tied to animation there too.
- Set a budget and guard it. Agree on startup time and frame targets for the recorded journeys, then check them before each release. Without a budget, speed slides back one harmless looking change at a time.
The same findings come up across very different apps. Startup is the most overlooked, because teams test with the app already warm. Lazy load screens the user can't see yet. Defer analytics and remote config until after the first paint, and skip large blocking reads from storage at launch.
Navigation comes second. A stack that keeps every visited screen mounted, each with its own timers and listeners, slowly drains memory over a long session. Unmount or pause screens that aren't visible, and clear subscriptions when a screen loses focus.
Native modules come third. Heavy work like image processing, encryption, or parsing large files belongs in native code or a background worker, not on the JavaScript thread. Our backend development services team often moves the heaviest processing to the server so the phone never has to do it.
Be careful with over the air updates. Services such as EAS Update let you ship JavaScript changes without a full store release, which helps with urgent fixes. They don't replace testing, and store policies still apply. Give each update the same release checks as a store build, and keep a fast rollback ready.
What should you check before a React Native release?
Check the recorded journeys from the audit against your budget, on the same mid range device, in a release build. If startup or frame rates slipped, find the commit behind it before you ship. Then make sure crash reporting captures JavaScript errors with readable stack traces. That means uploading source maps for every build.
Last, test on both platforms with real network conditions. A screen that's smooth on office Wi-Fi can stall on a weak mobile signal while it waits for data it should have cached on an earlier visit.
Release checks for React Native apps stay manageable once they're automated. Run the journey recordings in CI on a device farm or a spare test phone. Compare timings with the last release, and fail the build when a budget breaks by a clear margin. Manual checklists get skipped after a few busy weeks.
When should you bring in outside React Native help?
Outside help pays off at two moments. One is right after a launch that felt slower than the prototype. The other is just before a large feature that will touch lists, animations, or navigation. Either way, the team knows something is off but has no time to profile while shipping.
It's a poor permanent crutch. A good engagement should leave a shorter list of problems and a team that can find the next one alone. That's why budgets and CI checks matter more than any single fix in React Native apps.
Pattem Digital's React Native development services team can run the audit, fix the top items with your engineers, and leave the budget checks in place so the gains hold over the next few releases.
Hire React Native Developers
Our React Native engineers profile, fix, and extend apps that are already in users' hands. They work in your codebase on lists, images, animations, startup, and native modules, and leave behind budgets your own team can keep checking.
Build Operate Transfer
We build and run your React Native team, document the app and its release process, then hand the team to you.
Offshore Development Center
An offshore development center that ships React Native features and fixes on your release schedule and standards.
Product Outsource Development
We deliver a complete React Native app, from architecture and native modules to store release and speed checks.
Managed Services
Crash monitoring, dependency upgrades, performance budgets, and store releases run under an agreed service level.
Global Capability Centre
A Global Capability Center that owns mobile engineering for several React Native apps across your business units.
Capabilities of Our React Native Team
Profile release builds and find the thread behind each stutter.
Tune long lists, images, and navigation for smooth scrolling.
Build native modules for heavy work in Swift and Kotlin.
Set performance budgets and automate checks in CI.
Engineers who find why a React Native app feels slow and fix it in your codebase alongside your team.
Find Out Why Your App Feels Slow
Share a release build and the screens that worry you. We'll run the Thread Time Audit and send back a ranked list of what to fix first.
Share Blogs
Authored By
Related Blog
.NET MAUI Development
Develop cross-platform desktop and mobile apps from a single codebase for reliable business operations.
