Advanced MySQL 8

Traditional locking versus optimistic locking

Group replication uses optimistic locking. In a traditional locking mechanism, if two transactions are updating the same tuple, the second transaction waits to read the value until the first transaction commits. In a group replication mechanism, those two transactions are happening on separate machines. Group replication optimistically assumes there will be no conflicts across nodes, and in this phase, no communication happens among nodes. Cluster-wide conflict resolution happens only at commit, during the certification process.