We do 4-day (32 hour) work weeks at Monograph, and we've been doing it for 3 years now. I believe we're one of the only companies in SF that are advocates for working less, but more productively.
Similar to Microsoft, we only have one 45-min meeting each week and then everything else is heads down work.
To maintain efficiency, we also have strict Slack protocols in place to keep everyone in deep work throughout the day. (No @ or DMs, everyone checks Slack at 11am and 4pm).
The major downside so far has been customer support, which the founders still manage to maintain our response rate.
Oh and we're hiring! If you're frontend engineer and like 4-day weeks + side projects, reach out directly email@example.com