Most performance problems in web applications come down to one thing: the database.
With Django, the situation is no different - in fact, in some ways it's even worse than that of our ORM-hating colleagues. Database performance tuning in Django involves a dizzying number of ORM API methods (defer, prefetch_related, iterator, and many more), mysterious alphabet letters (Q, F?!), and all of this rests on top of the already complex machinery of SQL queries and indexes.
I'm going to make a bold claim here: The only way to master Django is to master database performance. The difference between junior, mid-level, and senior Django engineers is usually a function of this mastery.
And to fully master database performance with Django, reading through API documentation is not enough. You need to become an expert. Here are some examples of what an expert knows that this book will teach you:

How to use profiling and measurement tools like New Relic, Django Debug Toolbar, and database query plans to see exactly how badly a query performs in production

How to eyeball a query and know exactly the right index to speed it up (a covering index with INCLUDE? a partial index? a GIN index? You're going to tell me by the end of the book because YOU will be the expert)

How to use advanced techniques like server-side cursors with iterator(), custom Func() expressions, and keyset pagination with row comparisons to churn through millions of rows of data with ease

You will learn all of this and more through over 160 pages, 60 examples, and 30 quiz questions. By the end, you won't ever think of a Django ORM query the same again: it will exist simultaneously in your mind as an operational metric, ORM syntax, generated SQL, and a database execution plan. Because you will be an expert.

I can teach this because I have over ten years of experience working with Django and relational databases, both as an application developer and a platform engineer building databases as a service for [...] and IBM Cloud.

And did I mention that you're going to have fun? Yes, you read that right. This book is chock full of awesome fantasy art including a map of each chapter's core concepts. Why fantasy art? Because I play tabletop role-playing games and I require books to be fun.

So gaze upon the Sacrificial Cliff of Profiling. Get lost in the Labyrinth of Indexing. Ransack the Crypt of Querying. Then get back to saving the world from unbounded queries!