In my opinion, there is a lot of pretentiousness and arrogance in the engineering department, especially for the senior members and management. As an engineer with only a few years experience, asking questions and trying to seek guidance was a difficult task to achieve. Often times if I were to ask a "stupid" question, I received a strong sense of being looked down upon and judged before being given a hesitant answer that only answered my question at the surface level. In other words, they didn't care about me or my growth as a software engineer. The "flex Fridays" are heavily advertised, as having your Friday to work on other projects, catch up on work, or take off completely. But it's really a ploy to entice candidates to accept the offer (disclaimer, I am strictly speaking as a software engineer).
Being a startup, a lot is expected of you. Long hours, being logged on well into the evening hours, and working weekends. This would all be fine if you knew what you were getting into, but it's never said, only expected. Honestly, they preach a work life balance, which is even more frustrating since the reality is nothing of the sort.
Like I said in the pros, if software engineering is your only interest, you're a software development wiz, or you just absolutely love designing and thinking about databases, by all means, this is for you. But if you're someone who is looking for a job that will give you back what you put in, be cautious. I advise you to ask skeptical and challenging questions in your interview process. And ask what team you will be joining and make sure you speak with your manager before accepting the position to ensure you will have a healthy working relationship.