Pros
Inspiring product. The "culture" can be fun and there are all the regular startup perks. It is exciting and Karaoke is a sport here and people play it well. There a tequila tastings even though they might be fully work appropriate.
Cons
Management is a mess and as more people join it seems to get worse. Across organizations high performing people get undermined or demeaned and the choice of who promoted is confounding. My management has a massive temper and is uncommunicative even in direct inquiries. When in person my manger has a tendency to lashes out including anger and yelling. In my situation my direct management is pretty offensive both in how he treats other people and how he treats me. If you are looking for good working relationships or to have an impact and you are not already buddy buddy with someone at Fastly I would think hard before joining.