Pros
I was the 2nd SDR hired by Fastly and during my two years at the company I saw the Sales Development team grow from 2 SDRs to 8 SDRs. The team has a lot of great people that are very friendly and good at their jobs. The SDR manager is the best manager I've ever had the privilege of working with in my career. He's very hands off and lets you be yourself, which I greatly appreciated it and I believe is the primary reason for my success at the company. If you're on the fence about joining Fastly and you're applying for the SDR role, I suggest you go for it. You won't regret it.
Cons
While there is a biannual performance review for the purpose of giving and receiving raises, there's currently no tangible plan that outlines a promotion track for SDRs at Fastly. The odds are against you if you want to be considered for a promotion based upon merit alone. You need to befriend a reputable manager who will give you their blessing and take their personal time to help train you and to champion you internally to Sales Leadership. The hiring manager and recruiter will tell you there's opportunity to be promoted from SDR to a closing sales role but as of the time of this writing, they're absolutely lying to you.