Addressing web-scale workloads and taking advantage of multi-core processors, VoltDB is the in-memory, distributed version of DBMS that addresses scalability, high-availability, ACID compliance and speedy performance without resorting to workarounds like MySQL with memcache or using NoSQL alternatives like Cassandra. No more sharding the database or learning key-value mechanisms. Developers can use a subset of ANSI SQL and Java for transactions implemented as stored procedures.
If there’s a DBMS meant to be used for cloud environments, VoltDB is a key contender. You may download an open source version here.