The interview process is one of the best aspects of the company.
Generally Software Developer interviews are long and stressful.
At ESR, you chat with the CTO, talk about your experience, show off some of your code.
After this, you have a second round with the dev team. You talk to them about your experience similar to the previous interview. They give you a take home assignment that involves working with one of their test APIs.
Finally, you interview with the CEO to discuss benefits and salary. This is the worst part of the process because you will get low balled for salary.