circuitbreaker, service discovery,profiles, how to config db, ways to commuinicate b/w microservices, why microservices, how does springboot handle dependency injection, what is synchronization, functional interface in java, optional , arraylist vs linkedlist, internal working of hashmap, controller advice,garbage collection, finally, throw vs throws, how is security done in APIs, ci/cd, get even number from a string that has chars, ins and special chars