PERFORMANCE · REACT NATIVE · 60FPS
Your app is slow. I'll tell you exactly why.
Performance audits, C++ JSI migration, cold start optimization, and 60fps on budget Android. 50K DAU production experience.
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By Amit Chakraborty — Kolkata, India · Remote worldwide
What you get
- Performance profiling & audit — Flipper traces, Hermes sampling, Reanimated frame drop detection, and custom Sentry metrics that catch regressions before users report them.
- C++ JSI native module migration — Move hot-path logic off the JS bridge. 10–15× faster for scoring, ranking, image decode, and ML pre-processing.
- Cold start optimization — Hermes bytecode precompilation, lazy screen loading, inline requires, and startup sequence restructuring. Measurable TTI improvement.
- 60fps on budget hardware — Reanimated 3 worklets for gesture, off-thread image processing, FlatList virtualization tuning. Tested on ₹8K Android phones.
- Core Web Vitals for React Native Web — LCP, INP, CLS optimization for React Native Web and Next.js hybrid apps. Lighthouse 95+ achievable.
Proof
- Vulcan Eleven (50K DAU) · 60fps on ₹10K phones — C++ JSI modules for contest ranking, Reanimated worklets for gesture, zero cross-bridge allocations during live matches. 50K peak DAU, zero frame drops in production.
- Synapsis Medical (HealthTech) · 4h release cycles (down from 2 days) — CI/CD overhaul, build parallelization, test suite optimization. Release confidence went from 'fingers crossed' to 'automated confidence'.
- MusicX (Audio Streaming) · 60fps audio visualization — C++ audio processing pipeline with 60fps waveform rendering. Blockchain royalty calculations moved off the JS thread entirely.
How it works
- Performance audit (3 days) — Profiling, bottleneck identification, and a ranked remediation plan with effort estimates.
- Implementation sprint (1–2 weeks) — JSI migration, cold start fixes, rendering optimization. Measurable before/after metrics.
- Monitoring setup — Sentry performance, custom frame drop detector, regression alerts. The improvements stay.
Frequently asked questions
Can you optimize apps built with Expo?
Yes. Expo apps with custom dev clients support native modules and JSI. For Expo Go-only apps, I focus on JS-layer optimizations (memoization, virtualization, Hermes tuning).
How do you measure improvement?
Before/after Flipper traces, Hermes sampling profiles, and production metrics via Sentry. Every optimization is quantified with real numbers, not vibes.
What's the typical performance improvement?
Cold start: 30–60% reduction. Frame drops: 80–95% elimination. JS thread time: 50–90% reduction on hot paths moved to JSI. But every app is different — the audit tells you what's realistic for yours.