I'm turning 43 in a few months and estimate I have talked to some 50 companies since turning 40, the vast majority I passed on and only perceived one interview where I felt like age discrimination came into play. I landed my prior position just past 40, which was a small startup, and my current at a larger company a few months ago.

I do come off rather young in person, but my resume is clear about my work experience, graduation date and so on. Even with the one case where I suspected age discrimination was at play it was only after the fact when the recruiter said the company passed because they decided to go with someone more 'malleable' (for a sr. role, mind you) where the average engineer was probably about 25 yo.

Not saying it's not an issue, there's many reports out there of people experiencing it, but perhaps it's more restricted to the valley or not quite as common as implied. I say this as someone who was nervous about entering my 40s for this reason alone and have been pleasantly surprised to find it to be a non-issue for myself.