How to practice backend engineering.

On a recent call, I chatted with someone about backend roles in software engineering, and what folks actually do in those roles. More than just what do these folks do, how would you practice for this kind of role or prepare for interviews?

Roughly the sorts of work that backend engineers are asked to take on versus the work that any engineer might be asked to take on, three categories of tasks stand out to me as being both frequent and practicable:

Modeling and remodeling data - how do you de...