Abstract

Distributed databases power many of today’s web-services including those that provide governance, e-commerce, social networking, banking and healthcare. Distributed databases are typically composed of a geo-distributed set of replicas connected over the internet. The replication and geo-distribution allows the web-service to scale to a large number of concurrent users while minimising the user perceived latency. However, it is also a fact that network connections over the internet are slow, have limited capacity, and are often unreliable. When a network connection between replicas fails, as it invariably does, the simple single system image the developer has over the database is lost.

Under distributed databases, high-level guarantees provided by traditional databases such as strong data consistency and isolation is lost. This pushes the pain and confusion of inconsistent data reads and unreliable writes to the developers, and leads to consistency bugs in the web service, ultimately leading to poor customer experience and lost revenue. In this talk, I will present Quelea, a declarative domain-specific language that allows the developer to easily express and automatically enforce fine-grained application level consistency properties on a commercial off-the-self distributed data store. Based on the application’s consistency requirements, Quelea minimizes communication and eliminates unnecessary coordination between replicas.