Speculative Transaction Processing in Geo-Replicated Data Stores

This work presents STR, a geo-distributed, partially replicated transactional data store, which leverages on novel speculative techniques to mask the inter-replica synchronization latency. The theoretical foundations on top of which we built STR is a novel consistency criterion, which we call SPeculative Snapshot Isolation (SPSI). SPSI extends the well-known Snapshot Isolation semantics in an intuitive, yet rigorous way, by specifying desirable atomicity and isolation guarantees that shelter applications from subtle anomalies that can arise when adopting speculative transaction processing techniques. We assess STR’s performance on up to nine geo-distributed Amazon EC2 data centers, using both synthetic benchmarks as well as complex benchmarks (TPC-C and RUBiS). Our experimental study highlights that STR achieves throughput gains of up to 6⇥ and latency reduction up to 100⇥, in workloads characterized by low inter-data center contention. Furthermore, thanks to self-tuning techniques that automatically adjust the aggressiveness of STR’s speculation degree, STR offers robust performance even when faced with unfavourable workloads that suffer from high misspeculation rates