The Serial Safety Net: Efficient Concurrency Control on Modern Hardware
Summary
The Serial Safety Net (SSN) is a certification layer that can be layered on top of high-concurrency but weak isolation levels like RC or SI to achieve serializability without the performance penalties of 2PL or SSI. It uses per-transaction low and high watermarks to detect potential cycles, aborting when necessary, and offers a Safe Retry property to keep throughput stable under contention. The post discusses trade-offs, metadata overhead, handling of phantom records, and why SI+SSN may be preferred over RC+SSN for avoiding in-flight inconsistencies, while pointing to deeper journal versions and related work.