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      Principal Java Engineer Interview

      25 Mar 2025
      Anonymous interview candidate
      Dublin, Dublin
      No offer
      Negative experience
      Easy interview

      Application

      I applied online. The process took 1 week. I interviewed at Waratek (Dublin, Dublin) in Mar 2025

      Interview

      One long 2 hour discussion, first 45 mins were java code they want you to read and ask some questions, one of the panel member was a principal engineer, and the primary interviewer, and then all of the rest of time was a freewheeling no format discussion that i found quite weird, there were moments of total silence, i felt they did not know what to ask, they would ask random questions like git merge vs git rebase. The primary principal engineer was quite inexperienced and is more of a junior/senior engineer, and i felt he was not able to interview well, as he was short on skills and really did not have deep java knowledge, during discussion, he never followed up on any questions, when i tried to go deep, for the hashmap question, when i started going into internals of the implementation where the jdk hashmap impl switches from linked list to a red black tree, he went silent, there was a long silence, and then he moved on, i guess this was because he did not know that, and just wanted to ask basic junior java dev questions, he asked a question about serialization, but was not aware of serious serialization issues with java, to explain, i gave an example where the internal vm implementation when de-serializing a class totally avoids looking at the constructor, and so if there's conditions in the constructor those will be bypassed, and when i asked him, what would be the value of the instance if another process gets access to serialized class and modifies the instance value but when the class is serialized back by the vm the condition in the constructor is not looked at, and so you can have different instance values in the class, when the same class is serialized, i gave an example and asked him what would be the serialized value and he gave the wrong answer, maybe that hurt his ego, all in all, it's just a regular java shop, the team is not skilled at all and are behaviorally quite weird, i won't suggest even interviewing, the main interviewer it seems picked up some trick questions and asked those. the management is clueless

      Interview questions [1]

      Question 1

      sample codebase and then general discussion
      Answer question