MTC: Scalable Transaction Commit for Multi-Primary Cloud Databases

While compute-storage disaggregation provides elasticity to cloud databases, the prevalent single-primary model restricts write scalability and fault tolerance. Maintaining data consistency becomes a key challenge when multiple primaries handle concurrent writes, especially with hot data cached locally. This paper presents MTC (Multi-Primary Transaction Commit), a scalable and non-intrusive commit mechanism for multiprimary databases. The core idea of MTC is to decouple global transaction ordering from log synchronization. By enabling primary nodes to asynchronously prefetch Global Transaction Sequence Numbers (GTSNs) and assign them to locally completed transactions, MTC implements a highly efficient “check-thenreplicate” workflow. Following a pipelined, row-level conflict detection, validated transactions commit immediately with their logs broadcast asynchronously. Conflicting transactions, however, are rolled back locally with minimal overhead, fundamentally avoiding the network cost of broadcasting logs for transactions destined to abort. Our experimental results demonstrate that MTC significantly improves performance and scalability due to lower network overhead and more efficient conflict detection, even under high contention deployments.