The first step -task on devskiller platform, included questions with multiple choices, code review, and write unit tests for the given code, my hint for you for the unit test is to rehearse how to mock static classes second step - interview included your comments on the code, during the interview interviewer asked questions about hashmap, list, concurrency etc third step - system design, I was asked to come up with an architecture and I should have proposed some technologies to use, you should know many technologies and know how microservices work, how backend would communicate with frontend etc