react-native-threads VS JCTools

Use this if you can't offload that to a server so that your app may asyncronously request it. Do keep in mind that I did not use it, so I cannot vouch for how well it functions. I simply searched your question and found this to be helpful.

In React Native, every process has only one thread. Unfortunately, because of this, people often use the terms interchangeably. You’ll notice UI Thread, JS Thread, and React Native Modules Thread are actually all processes, and react-native-threads actually implements multi-processing.

Install some tool that would help you see the performance of your system, like a graph of the CPU usage, the top processes being used, disk activity/read/write, etc. Every time you run your program, glance at those numbers, eventually you'll develop an intuition. Basically write code and profile. A good exercise would be practicing with data structures, this site has an exhaustive list of them, find some stuff that's interesting then google the implementation, then build it yourself, test it, debug, profile, optimize, and understand the performance constraints. Eventually you'll develop better understanding and can compare between other people's works, optimizing them. If you want to go beyond, read some papers on lock-free algorithms https://github.com/JCTools/JCTools/tree/master/resources then read Brendan Gregg's blog and books. Read about how profiling tools work https://github.com/andikleen/pmu-tools/wiki/toplev-manual

If I fork this implementation's repo and then publish a release (of the forked version) with my own commits via jitpack.io (committing with Android Studio IDE).