From the course:
"In this challenge, you'll build a barebones SQLite implementation that supports basic SQL queries like SELECT. Along the way you'll learn about SQLite's file format, how indexed data is stored in B-trees and more."
So yes for B-trees, but it seems to end with SELECT and a basic WHRERE query, no joins or anything like that
Searching "USDS or 18F" helped google understand what I was looking for