[mjs]

Oh, I didn't realise much of Riak was in C, and the website now mentions Erlang a whole lot less than I remember. Still, in the technology stack http://basho.com/technology/technology-stack/ Riak Core seems to be all Erlang. Bitcask is possibly C--is that what you're referring to?

[fuddie]

Your language and line of questioning leads me to assume that you're perhaps not that familiar with Erlang.

Erlang has facilities for running native code within the VM (NIFs and linked-in drivers) and for interacting with non-Erlang processes in an Erlang like way (ports and c-nodes). Extending the VM via these mechanisms is not the default path but it's also not unusual - much of the standard lib is implemented via these mechanisms after all.

To answer your question, bitcask, ebloom, eleveldb, erlang_js and skerl all have c_src directories which suggests they're likely either all or in part implemented via NIFs or linked-in drivers.

EDIT: You might also find http://vimeo.com/17078993 interesting viewing.