It&#x27;s a lot of C++ today. In fact, they have open-sourced a lot of the in-house tools they use, eg bde: <a href="https:&#x2F;&#x2F;github.com&#x2F;bloomberg&#x2F;bde" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;bloomberg&#x2F;bde</a>