For this section, it's highly recommended to watch the lecture video sections. What follows are summaries of the content; following the visuals are more insightful.
Building a system to implement many different kinds of things in a repeatable manner lends itself to designing general specifications for information, and then generating pages as needed.
This concept extends towards testing - particularly important as the real world has no autograder and no definition of correctness beyond tests that you write.
Commit History Traversal
Using what you already know in 61B - representing graphs, doing a BFS - you can solve real-world industry problems! This was an example of finding what deployments contain a certain change, by adjusting how we might represent a graph and then doing a BFS while choosing specific data structures for runtime and ease of use.