AlphaSights no longer has the right to label itself as a start-up, they've been around for 10 years, but it still suffers the problems of one. The company focuses so heavily on recruiting fresh graduates that relevant experience takes a back seat.
With the vast majority of "managers" having only a few years working experience under their belt, anyone seeking career guidance or professional development is going to be sorely disappointed. Personally I've had 3 "Vice Presidents" promise sponsorship for professional qualifications only to have the offer rescinded after my acceptance.
Your manager will micromanage you and cannot, or will not, accept that you are a capable employee with a social life outside of work. Clients will email and call you at unreasonable hours with unrealistic expectations and you will be expected to deliver without question.
Expect constant interruptions to your work with pointless meetings about "business", "professionalism", and such when most of the staff are "Associates", a term here that means "Telesales staff".
Prepare to be constantly reminded by managers (who may only have 2-3 years working experience, and only at this company) about how much you learn about various industries, companies, and creating professional networks (by means on trawling LinkedIn and making a load of cold calls). Anyone who thinks they can become an expert on an industry by talking to a high level executive over the phone for a few hours is very naive.
On a personal note, I was forced to resign. Having decided that I wasn't getting the experience I wanted from AlphaSights I decided to confidentially inform one of the Vice Presidents. Within 2 weeks I was pulled into a meeting with a different Vice President who promptly promised a smooth exit for me. They promised to keep me in the loop when hiring for my replacement, including being involved in the interviewing and search process, but after a few months I was told by that same Vice President to commit to a last working day because they have hired someone. I wasn't even made aware they had begun the hiring process yet.