There will be MANY people interviewing you at once, depending on who's looking to mentor a new junior. The CEO, Sean, really trusts the input of his employees and everyone in the interview with him will ask you something (he's super involved in the day-to-day operations, and you'll see him on the sales floor every day). The vibe will be casual because the dress code is super casual, but don't be fooled: everyone here takes their job seriously and they're taking your interview seriously, even if they're in sweatpants and slippers. Although he's the one who is "officially" interviewing you, you will be hired by a senior running their own team and they are looking for someone who will work directly under them.