(db
[node]
[node ^Date valid-time]
[node ^Date valid-time ^Date transaction-time]
"Will return the latest value of the db currently known. Non-blocking.
When a valid time is specified then returned db value contains only those
documents whose valid time is not after the specified. Non-blocking.
When both valid and transaction time are specified returns a db value
as of the valid and transaction time. Will block until the transaction
time is present in the index.")