Dropbox changes terms
Dropbox is changing terms and now, for the security reasons, access to cloud will lasts for 4 hours only. After that you'll be forced to link the app to Dropbox again on all devices. Of course this changes makes Dropbox completely unsuitable for synchronization.
Initially Dropbox was temporary option, but proved to be very convenient so we used it for many years. But all ends someday and now, to be independent from other's rules and conditions, we've set up our own cloud server.
Server load is expected to be decent and this must be a managed server: someone should look after server, restart and update it when needed. It's not cheap, so there will be paid subscription for synchronization.
We understand that you may not want to store your database file on our server and made option to transfer current changes only, without the need to upload a whole database file to the cloud. Keeping a backup copy in the cloud is disabled by default. If this option is enabled, there will be changes history in cloud, but no more than one copy per day for the last week and one copy per week for the last month.