Core Java- OOPS concept in details with example, collection vs collections, array vs array list internal working , HashSet vs HashMap difference and internal working, linked list vs array list which one is preferred ? what if array list size is full how new element is added to list. Spring- what is auto wired? dependency injection? types of DI, difference between construction injection and setter injection. singleton and prototype difference. Rest api call, spring mvc architecture, @Qualifer uses. @Controller, etc different types of annotation used in spring MVC architecture. Last question was how to load huge data from Rest api to the DB if its loaded in DB at a time then the database will crash immediately in such case how you will handle the situation. They kept you waiting for 5 hours for an interview even if there is very few people. They only hire if you go through referral drive.