Databases are a core component of any software and a core subject in computer science. 

There are many excellent database resources out there. Still, you appreciate how efficient databases are once you dive into algorithms and data structures and implement them yourself. 

I'm currently reading Database Internals by Alex Petrov and Designing data-intensive applications. Both are excellent books that I've read multiple times, but I still need to grasp everything. 

I've started taking a hands-on approach. I will try to blog about my progress and critical lessons and share the source code. 

Please keep in mind that this will be very subjective writing, as I'm reflecting on my own experience doing that.

Here's an excellent video that summarizes the most common data structures for databases covered in both books.