Web Consortium (W3C) compiled APIs for use by KaiOS front-end developers and web developers. Contribute API implementations and bug fixing to open-source community. Improve system performance and save memory usage. Re-implement SystemMessage API (a KaiOS API) and improve it with Service Worker (a standard Web API). Leverage the advantage of off-main-thread implementation, save 80% of time per message receiving and drop usage of system memory in certain use cases. Troubleshoot issues in operating system level, experience multi-threads and inter process communication programming. Experience memory leaks and dead-lock