Theoretical - transactions -java propagation types for transactions -spring security: oath2, refresh token -bean scope: singleton, prototype, default -@component vs @service -type of injection: constructor, setter, which one and why one is better -400 error -PUT vs PATCH -object vs class -OOP principles -public vs protected vs private access -abstract class vs interface -anonymous class - default method -final var, final method, final class -try catch, finally -types of exception -types of join -database relations -db index

From basic concepts/best practices to architectural patterns, databases, message brokers, clouds, based on my professional experience,