easy way to get "the latest event of a type"; currently this is used in the follower worker, but it would be useful for #23 too
allow us to migrate to Postres in v2.0, where we can have static, simple and relational data types (even trees can be stored in a table)
allow us to abstract away watching for new event aggregates/validator messages, therefore removing wait/snooze periods; under the hood it can be implemented with redis pubsub or via postgres
this will help in many ways: