A months ago I published a write-up of building our our cloud sync in Polar: https://getpolarized.io/2019/01/03/building-cloud-sync-on-google-firebase.html htt

A months ago I published a write-up of building our our cloud sync in Polar: https://getpolarized.io/2019/01/03/building-cloud-sync-on-google-firebase.html https://getpolarized.io/2019/01/03/building-cloud-sync-on-go... Polar is basically a document management and annotation platform. You put all your reading in it and maintain it long term along with annotations, highlights, etc. Firestore is really nice in that you can target multiple-platforms pretty easily. There are SDKs for basically every platform. It's definitely not perfect but I'm pretty happy with the decision.