[7] Mesos, abstracts CPU, memory, storage, and other compute resources away from machines (physical or virtual), enabling fault-tolerant and elastic distributed systems to easily be built and run effectively. - http://mesos.apache.org/
Mesos was invented at UC Berkeley but developed and battle tested at Twitter.
[1] Heron, a realtime, distributed, fault-tolerant stream processing engine - https://github.com/twitter/heron
[2] Finagle, a fault tolerant, protocol-agnostic RPC system - https://github.com/twitter/finagle/
[3] FlockDB, a distributed, fault-tolerant graph database - https://github.com/twitter/flockdb
[4] Gizzard, a flexible sharding framework for creating eventually-consistent distributed datastores - https://github.com/twitter/gizzard
[5] Twemcache, a Twitter fork of Memcached - https://github.com/twitter/twemcache
[6] Twemproxy, a fast, light-weight proxy for memcached and redis - https://github.com/twitter/twemproxy