Q:

Software level architecture of Stack Overflow

I was going through this video: Architecture of StackOverflow - Marco Cecconi where he says there are few projects in the Stack Overflow solution. And this made me curious.
What is the architecture of Stack Overflow Solution directory and since the video isn't clear about the projects inside the solution, can anyone tell me what they are? And how each project is dependent on the other. 
EDIT This is not the same question as "what is stackoverflow built with". This question is specific to the software side of it, basically the Layered architecture of StackOverflow and the Visual Studio Solution directory.

A:

These are our projects, each one is a different product:

Stack Overflow (https://stackoverflow.com/, this site and all the *.stackexchange.com sites)
Stack Auth (http://stackauth.com/)
Stack Overflow API
Stack Overflow APIv2
Stack Overflow Mobile (private API for mobile apps)
Stack Server, the backbone server code for our Tag Server (among others)
Socket Server, web sockets server
A Unit Tests project
A project for build files

Layering is done mostly using folders within each project. If we have common dependencies, they are productized and extracted to separate solutions using an internal nuget (or external if we open source it).
There are a few dependencies across projects, mostly to share code that is not productized.
Here's the dependency graph:

