Reddit was one of my best interview experiences. Everyone at the office is really passionate about the work and it definitely shows. I would highly recommend it to anyone who gets an offer. They generally do 3 interviews (1 whiteboard, 1 coding, and 1 specific to the role). Study up on DS&Algs, OOP, and system design&architecture but make sure your implementation skills are up to par as well (don't just focus on whiteboarding).