[API] Ability to fetch recent changes to the contact list
At PieSync we would love to offer a two-way contact sync between mailgun and all our other contact apps (you can find the list of currently supported apps on https://www.piesync.com/connections/).
However currently we can't do this, because the API does not deliver us an efficient way to get recent changes to the contact list (recently created and updated contacts). If the API would add one of the below 3 methods, we would be able to do so:
1. Fetch contacts updated after given time (filter the contact list by updated time).
2. Fetch contacts sorted descending by updated time (sort the contact list by updated time).
3. Register a webhook that sends us notifications for contact creations or updates.
Note that we cannot simply fetch all the contacts each time and check the creation/update datetime for all these contacts each time as:
a) we're a real-time sync platform, so we require these calls to be efficient
b) we don't actually store the full contact data at PieSync, so we'll have to keep everything in memory, which is terrible for performance.
c) it's simply not API efficient, not robust