Online and Offline POS

[SourabhSK]

I am looking for a PWA/Cache expert who can work on the existing POS web link when the internet is not working the POS module must work normally and when the internet is up automatically the DB in the server must be updated accordingly
PHP framework - Codeigniter
Database - MySQL
Cloud - AWS
POS Module - .JS
We want the online web application to run even if there is no internet, i.e. if the internet is not available the data should be stored in the cache and once the internet is available the data should be pushed to the online server.