starting from react-native version 0.59 react native provided support for 64 bit. https://facebook.github.io/react-native/blog/#updated-jsc-means-performance-gains-and-64-bit-support-on-android
Though my application is using old react native version (0.39) and upgrading to 0.59 is very huge task. After August 1, 2019 I will not be able to update app in google play store if my app didn't support 64 bit CPUs.
This is very serious matter. Does anyone have any workarounds?