Check out: - designing data intensive applications

https://www.oreilly.com/library/view/designing-data-intensiv...

- Database internals

https://www.oreilly.com/library/view/database-internals/9781...

If "Readings in Database Systems" is your cup of tea you should probably consider

* Database Internals (https://www.oreilly.com/library/view/database-internals/9781...) - very recent and of manageable size

* Database System Concepts (https://www.amazon.com/Database-Concepts-Abraham-Silberschat...) - specifically, the chapters on storage and query processing, it's a huge volume otherwise. Also, "Database Systems: The Complete Book" is basically an older version of it.

Should mention the newer OReilly "Database Internals" book here: https://www.oreilly.com/library/view/database-internals/9781...