Learning how to design scalable systems will help you become a better engineer
System design is a broad topic. There is a vast amount of resources scattered throughout the web on system design principles.
Everything is a trade-off.
You should be familiar with the classic "getting started" architecture. This is what most applications get started with, a simple web server that communicates with a single database and is exposed via a public DNS.
This is more than enough to get an application working as fast as possible, but you'll start finding limitations soon.
