I spent 8 years in engineering at MS in the 2000s--it was no worse or better than any other tech company. There was never an explicit expectation to work more

I spent 8 years in engineering at MS in the 2000s--it was no worse or better than any other tech company. There was never an explicit expectation to work more than 40 hours, and most managers were good about not pressuring people into disturbing work-life balance. But, at the end of the year you were calibrated against all of your peers and WLB was not a criteria that mattered. If you just put in your 40 hours you probably wouldn't get fired, but you definitely were not going to be promoted when compared to the people cranking out more work per week. There was a big divide with the younger, fresher folks working all the time (and making their work very visible). Once you were a senior dev you kind of had a choice to make--if you wanted to keep a high 'promotional velocity' you had to keep working >40 hour weeks or be left in the dust. If you didn't want to climb that ladder then it was totally fine but you would never be promoted beyond another level or two. I knew folks who were senior devs for 10, 15, or even more years. In contrast the partners/high performers were all regularly getting promotions every 2 years or less and absolutely none of them I knew worked less than 60-80 hours a week. To get promoted up to principal and beyond levels required having a consistent history of promotions every couple years--there was no way to really pause or slow down without stopping your entire career development. From my friends still left there I don't think much has changed over the years. It's a somewhat subtle system where managers and HR can proudly point to never requiring people to work crunch time. They can trot out plenty of 10 year senior engineers to give quotes and talk about how it's so great to just work 40 hour weeks. But at the end of the day if you want to be successful and rise up the ranks at MS, you are going to be working all the time, period (at least until you reach partner level).