I'm 38. And I feel enormous pressure to be smarter than everyone around me to be relevant. People expect you to be incredible both at management and engineering as you get older. I'm very lucky my career path has given me opportunity here, because but for a few chance encounters I'd be much, much worse at both and that'd be awful. I'm quite worried about what people will expect of me when I'm 45. I'm working hard to add data science to my resume because I think that "mathy" roles have less discrimination against them than pure engineering roles, and I want to stay ahead of it.
I do a lot of stuff that is tactical as well. For example, today I'm wearing a uniqlo-nintendo collaboration t-shirt with Pikachu on it. I'm doing so on the day I'm giving an interview. Because I know, tactically, this shirt is silly and irreverent and paints a picture of someone younger at heart.
And maybe that is naturally me (pika pika, ban lylat!) but I'd be lying if I didn't continue to do it tactically to appear more relevant and "with it".
What's interesting to me is that outside of the SV startup world, every computer scientist and great engineer I respect is a person over 40. Especially in academia, where women and men of astounding intelligence are doing work that in 10 years will probably reshape the industry (put forth, naturally, by breathlessly enthusiastic 21 year old "devrel" folks mis-attributing the work of 2 generations of academia to the brilliance of the senior technical staff at that company).
So yeah, it sucks. It's real. And there is a reason in the older white male-ish segment you find more awareness of other types (gender, racial) discrimination in the industry: people over 40 directly experience age discrimination and it's not at all theoretical even to white men in that cohort. If it can happen to older white dudes, it surely can happen to anyone else.