Count your worklets before you start deleting your own code
Hermes V1 attaches 512KB of debug metadata to every worklet, so simply importing Reanimated can add tens of megabytes. Here are the three numbers to count before blaming your own code, and how to choose between the four available fixes.
Measuring Hermes Bytecode Delta Updates: One Added Module Cost 29x More Than One Changed Line
I measured OTA delta sizes against a 2.4MB Hermes bytecode bundle. Changing one line cost 2,104 bytes; adding one module cost 61,197. The widely repeated advice about stable module IDs turned out to matter least.
When your Rork app's production crashes arrive minified — wiring Hermes source maps and debug IDs into Sentry
Rork-generated Expo apps run on Hermes, so production crashes often arrive as index.bundle:1:284913 with no function names. Here is how to wire Hermes source maps and debug IDs into Sentry so your stack traces become readable.
Why Your Prices Show as “¥1234” on Some Phones — A Formatting Layer That Doesn't Trust Intl Alone in Expo
Same code, yet one device shows “¥1,480” and another “¥1480.” In Expo / Hermes, Intl leans on each device's locale data, so output can drift by OS and engine. Here is a resilient formatting layer that centralizes currency, number, date, and timezone handling and falls back gracefully where Intl is incomplete — with working code.
Two Months of Rork × Hermes in Production — Cold Start and Memory in Real Numbers
What actually happens to cold start, memory, and crash rates after running Rork-generated apps with Hermes enabled in production for two months. Field notes from an indie developer with 50 million cumulative downloads.
Staged migration of a Rork-generated RN project to the New Architecture — notes from running six wallpaper apps in parallel
An implementation log for incrementally enabling Fabric and TurboModules on a Rork-generated React Native project, validated in parallel across six wallpaper apps. Covers flag design, compatibility triage, and KPI comparison based on actual production data.
How to Track Down 'undefined is not an object' Errors in Rork — Fast
Read Hermes' 'undefined is not an object' error correctly in Rork — five typical causes with code, plus debugging steps when stack traces look unhelpful.
Getting Started with Latest Performance Optimization Techniques in Expo SDK 55
Comprehensive guide to Expo SDK 55's Hermes V1, EAS build caching, and modal improvements. Learn the latest performance optimization techniques with implementation examples.