There are 3 main stages; an online test, an HR phone interview, and an on-site technical interview, although there may be other requirements depending on the role. For the most part, all stages are straight-forward and both interviews are quite flexible. For the on-site case study, expect an intense line of questioning after the fact that could go for as long as two hours. Technically, it's not difficult, just make sure you're able to give explanations for what you did/would do if you had another go.