For performance, go to page 5: Indexes
An index is an old technique used in books to quickly find pages or chapters of different terms. It is heavily used in computers and as a developer, you probably use it every day.
This talk will guide you through the world of index types, how they work, and why it is they make some things so damn fast. By knowing how they work under the hood, it will make you use/configure them more wisely and even get more performance out of them.