Barclays Software Engineer in Prague: a Number of Islands style graph problem, SQL, OOP and multithreading questions, then a leadership round

I applied for the software engineer role based in Prague. The process moved along fairly quickly. I went through three interviews: the first was just an introduction with some normal behavioral questions, why I wanted the job and stuff like that. Next involved live coding and technical questions. Third round was leadership and more behavioral questions.

In the technical interview they asked a graph problem, similar to LeetCode's Number of Islands and then asked about time and space complexity of my solution. I could pick any language I wanted for that. Then they tested SQL knowledge, stuff like joins, indexes, partitions, and I was asked to write a query to retrieve employee data based on a table they provided.

They asked some technical questions on OOP and multithreading too, and some system design basics. The most difficult question I remember was to explain the difference between a ThreadLocal variable and a shared variable in multithreading.

Last round was all behavioral and leadership related questions. This was stuff I'd prepared loads of, make sure you can structure every answer with STAR method and it's easy enough, and be able to talk about a time you took ownership of a feature yourself.