Content update every 30 minutes.
firebase realtime database, nodejs RESTful API from firebase function.
resources
https://cron-job.org
https://firebase.google.com/docs/database/web/save-data#write_data_offline
https://github.com/dandv/firebase-db-web-offline
https://dandv.github.io/firebase-db-web-offline/
build by cl.mt