It was a phone screen, the panel had two people, one was an agile coach and other was a senior software development engineer. The interview started with agile coach and the the other interviewer was late to the interview, so we kept waiting for 5 mins, the senior engineer was close to rude, he suddenly asked me to share screen and open my IDE on my desktop(I was never informed my own IDE would be used)..asked me to write a simple program and a test case on Spring Boot, i did that, and ran the Spring Boot app, no questions there, then he asked a few basic Java questions, all answered, after a few minutes, I understood that the senior engineer is not technically as skilled and was not an experienced interviewer I have 10 yrs of technical dev experience and I was asked a particular question about removing an element from an ArrayList while I was traversing it, it was a simple answer i.e Concurrent Modification Exception, I also gave him the alternate solutions i.e iterator and CopyOnWriteArrayList...now I went ahead and started discussing with him if there are multiple threads and they are using iterator remove, he then said a CME would be thrown which was wrong and I mentioned the same CME is probabilistic and not deterministic and you should never rely on CME..I was shocked...such a senior engineer does not know basics of Java...by that time I had made my mind about Mastercard...it's just all marketing stuff and fluff..the engineering is not nearly as good, they are just running on marketing and once competition comes..will be difficult for Mastercard...and guess what..the HR never even came back...although I didn't probe the HR..but that says something about HR function as well..it's the same story...big corporate running just cos of marketing and no competition..

Most difficult question asked was Concurrent Modification Exception