Boost Android Performance Using Hermes

Instawork's Android app was taking 5-6 seconds to start while iOS clocked in at just 1.5 seconds. That performance gap was killing their user experience on low-to-mid range devices.

The Instawork engineering team tackled their React Native Android performance problem by upgrading from v0.59 to v0.61 and switching from JavaScriptCore to the Hermes JavaScript engine. This case study breaks down their migration process and the impressive results.

Key Takeaways

• Startup time dropped from 6 seconds to 2 seconds (67% improvement)
• APK size reduced from 28.6 MB to 19.8 MB
• Memory usage decreased from 206 MB to 141 MB during login flow
• Installation size dropped 28% (from 64.86 MB to 46.85 MB)
• Hermes requires only 3 lines of code to integrate

The team also integrated automated performance monitoring into their QA process on Browserstack to catch future regressions before they ship.