1. A method comprising: receiving, at a first time, a particular start transaction record; adding the particular start transaction record in a list, wherein the list comprises zero or more start transaction records that were added to the list before the particular start transaction record is added to the list; receiving, at a second time that is later than the first time, a particular end transaction record that signals an end of a transaction whose beginning is signaled by the particular start transaction record; determining whether the particular start transaction record still exists in the list; in response to determining that the particular start transaction record still exists in the list, removing the particular start transaction record; and in response to determining that the particular start transaction record does not exist in the list, sending the particular end transaction record to one or more apply processes.