We scale the database back-end in dynamic content cluster servers by
distributing read-only transactions on a set of lightweight database replicas
while maintaining 1-copy-serializability. This is contrary to conventional
wisdom in replicated databases which says that one could have either 1-copy
serializability or scalability, but not both.

The key to scaling is a novel integrated fine-grained concurrency control and
data replication algorithm called Dynamic Multiversioning that provides
fine-grained distributed concurrency control at the level of a memory page
across a database cluster. We exploit the different distributed data versions
that naturally come about as a result of asynchronous data replication in order
to increase concurrency by running conflicting transactions in parallel on
different replicas.

At the same time, the serialization order is determined using fine-grained
concurrency control at a master database and enforced through a version-aware
scheduling technique. Our technique does not put any crucial data in the
scheduler, which permits easy reconfiguration, without loss of data, in the case
of single-node failures of any node in the system.

Our measurements show near-linear scaling up to 8 databases for the browsing,
shopping and even for the write-heavy ordering workload of the industry-standard
e-commerce TPC-W benchmark.