What happens if you access the database simultaneously from different browser tabs? Also, is there some eventing mechanism to push messages through the database between tabs?
It works fine. Transactions prevent conflicts. And you can even do schema upgrades because there is built-in versioning, and it provides events to let you handle when a version change occurs in another tab.
Also, is there some eventing mechanism to push messages through the database between tabs?
No, you have to do that yourself.