So the DVM's typically cache on the DVM itself? 

Do they actually store data? Or just "pass-through" the events and links to the end relays where the data lives on? Just in a processed, pre-packaged order?

Does Amethyst use DVM's for their DM Push Notifications? Or just typical GCM/Cloud etc? Seems DVM's could maybe run a push notif service.... 

 There's pokey for push notifications! Check it out.

Some DVMs just fetch from relays. I store the last 2 days of notes in a local database and search there. 

 Will check into all these. Thanks a bunch man. 🙏