In my first week on the job, I was tasked with speeding up a site that was incredibly slow. And when I say slow, I mean REALLY slow: 40 seconds or longer to save a single post. 20 seconds or more just to get to the post editor.

Spoiler: We got it to work! And this is the story of how we fixed it:

We dug through endless lines of code.
We read some fantastic resources on the topic.
We spoke to our friends in the community, who are experts in their respective fields.

The technical details of this talk include:

xhprof with a custom addition that I wrote.
The filter ‘posts_clauses’.
The function ‘dbDelta()’.