To make it to the first interview stage, you must complete a CodeSignal assessment. From my experience, the score isn't as important and I think Block resume screens after the assessment. After that is a series of 3 pair programming interviews. You are paired with an engineer for an hour who gives you incremental problems that slowly build up. I loved that the problems start small so that you don't get overwhelmed or have to test a hundred lines. The problem difficulty is from easy to medium and the engineer is there to help you if you get stuck. The idea is to see how well you're able to pair program and problem solve. The problems aren't Leetcode style but they do require knowledge of algorithms and data structures. The problems get harder with each interview stage.