Ageism is a problem, especially in Start-up companies in Silicon Valley. Hiring Managers are scared of older employees. But, one can overcome by applying lot, stay in touch with latest technology and adapt any environment.
Don’t apply where they are looking for “Rock Star”... it means they are looking for kids for coding and running around with “Codewith....” T-shirts.
Even when I was younger I avoided applying to places which touted their foosball table. It seemed like they were trying to compensate for something.