I'm in my 40's have been with the same company (FAANG) for over a decade. I'd say a majority of the management (including engineering) is in their mid-30's to 50's. It looks like the entirety of the senior management in engineering in my org is in their 40's.

There are fewer individual contributors in their 40's, but I know several (some moved from manager back to IC, others stayed IC).

Maybe this is a bigger issue at startups, where the founders are in their 20's?