The Architecture of Open Source Applications (Volume 1) Riak and Erlang/OTP Francesco Cesarini, Andy Gross, and Justin Sheehy Riak is a distributed, fault tolerant, open source database that illustrates how to build large scale systems using Erlang/OTP. Thanks in large part to Erlang's support for massively scalable distributed systems, Riak offers features that are uncommon in databases, such as