… empty

If an empty map-name is written, PynamoDB removes the entry from
the dict (which is fine), but upon reading it fails validation as
the field is not there. By allowing nullable map_name, this is
fixed.

In AWS the DynamoDB table names are per region, meaning that if
you run staging and production in the same account, they would use
the same database. this is unwanted of course. Allowing to set a
prefix resolves this issue.

While running the master-server for a while, we gathered enough
data to balance the privisioned RCU/WCU better, resulting in a
more responsive master-server.

As multiple instances start up at nearly the same time, they would
all start their stale-check on nearly the same time. This is both
unwanted and gives stress on the database server.