The first interview stage was way too easy, almost feeling wrong. They ask you to prepare for 90 minutes for a take home exercise, but it barely took me 5 minutes. The second stage had a pair programming exercise which was a bit more challenging, asking to use trees or recursion.
The third stage was again some questions and some pair programming exercise. The first question was how a ConcurrentHashMap works internally, very specific and not everyone knows that, but ok. Moved to questions as time complexity inside different Maps. And finally something about GC's. The exercise part was one of those terrible online tools experience. No debug, no running the code, no auto complete. An algorithmic question, full of edge cases, with some 20 minutes to solve it. Lastly, a question about how to turn a list immutable.
Overall, two first stages too easy, third stage not such a good interview experience.