1. A concurrency control system, comprising: a memory; a record component that creates intention records from completed transactions generated concurrently on a distributed and shared log, the intention records describe the results of the transactions and include updated state of modified data items, the intention records are appended to the shared log and deterministically processed according to a sequence in which the intention records are appended, wherein the intention records are confluent trees that define transaction effects and dependencies according to structure and version information for each intention record; a meld component that merges an intention record with related last committed database state to create updated database state and prevent merging of the intention record with the last committed database state when there is a conflict detected, wherein the meld component generates an ephemeral intention record in response to melding a concurrent intention record and maintains the ephemeral intention record when reachable by an executing transaction; and a processor that executes computer-executable instructions associated with at least one of the record component or the meld component.