  In a geo-distributed database, data shards and their respective replicas are
deployed in distinct datacenters across multiple regions, enabling
regional-level disaster recovery and the ability to serve global users locally.
However, transaction processing in geo-distributed databases requires multiple
cross-region communications, especially during the commit phase, which can
significantly impact system performance.
  To optimize the performance of geo-distributed transactions, we propose
Decentralized Two-phase Commit (D2PC), a new transaction commit protocol aiming
to minimize the negative impact of cross-region communication. In D2PC, we
employ multiple co-coordinators that perform commit coordination in parallel.
Each co-coordinator is responsible for collecting 2PC votes and making a
PreCommit decision in its local region. This approach allows for the concurrent
invocation of multiple cross-region network round trips, and each region can
conclude its concurrency control locally before replication is complete, thus
significantly reducing the chances of blocking and enhancing system
concurrency. Moreover, we propose the bypass leader replication reply method,
leveraging decentralized co-coordinators to bypass the leader for message
transmission, thereby reducing the commit latency. Experimental results have
demonstrated that D2PC can reduce commit latency by 43% and improve throughput
by up to 2.43 times compared to the existing alternative geo-distributed
transaction processing methods.
