This is exactly what I'd like to do now that I'm in my 60s. I'd still like to work for several more years, but not full time. How did you arrange this? It seems to not be common in tech.
It was mostly accidental: first, I took a 3 month leave of absence to explore a midlife crisis. I came back announcing I'd like to go half-time to do a masters degree which my company was okay with, and when that was over, I just never went back to full time and my company was okay with it.
I guess and hope that simply directly asking for this is another strategy (and what I plan to do if I ever lose this job); otherwise, performing the above sort of misdirection, consciously, might also help justify the exception for management and peers.