State of interviews for backend related jobs

So I am actually working as Embedded - C++ engineer but in my free time I try to learn more about backend engineering by developing small programs with Java or Go, experimenting with their popular frameworks. The question I have is concerning backend development in general but I will give an example on Java.

Java (and Spring in general) is insanely verbal for me. I was wondering if at one point I wanted to do a career pivot, what kind of interviews would I face? Do I need to memorize the syntax at deep level? Every annotation? Or should I focus on high level design, such as how would I use core services with JPA on a given problem definition? I am hoping the answer is not "just grind the leetcode with java".

Ahh, also I am mainly interested in EU market.