(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.")