Since July of last year, I have been coding a metaverse-server for the Vircadia virtual worlds. The Iamus metaverse-server acts as the coordination point for the independent domain-servers which host the virtual world space.
When High Fidelity open-sourced the code for their virtual world, they kept the central coordination services private so a new service for accounts and discovery was needed.
In addition to the written documentation, I created a video walking through the internals of the code:
This should give anyone modifying Iamus an good start.