The best way to learn something is to do a deep dive and present/share it with others. Repeat this cycle. Make it a regular habit.

This could be in the form of a tech blog or giving a presentation to your team. There are also meetup groups, social media, and other outlets. Mentoring junior developers is another great way to stay current.

If you've been focused on front end for a while then try giving a talk at your company about something orm, db, or api related. In doing research you will learn, and you'll find yourself digging for more information to answer potential questions.

In short: help others learn. You'll learn a lot yourself along the way.