I'm a dev at one of the big-name tech companies. I like the job for many reasons:


I do interesting work on a cool product
I solve challenging problems and use a lot of high-level skills (quantitative, creative, writing, presenting)
It pays well


The problem is that I feel I need a more relaxed atmosphere (shorter hours, less performance pressure, and more flexibility), in order to free up time for other pursuits and reduce stress. The ideal would be a job that's around 30-35 hours a week, where there is flexibility to work more or less in a given week. Can anyone suggest where to look for a job like this, where I wouldn't have to sacrifice too much on the above points? (Obviously I would have to sacrifice pay.) My employer does not generally offer part-time employment.

The closest thing I can think of is when I did summer internships at my university's CS department. The work was very intellectually challenging, but if I needed to go home a couple hours early or get flexibility on a due date, nobody batted an eyelash. However, I'd like to find out if there are alternatives to academia since from what I've seen the pay there is a gigantic drop from what I'm currently making.

I've done freelance development before, but I do like that as an employee of a large company I have a lot of things taken care of for me (e.g. benefits and guaranteed stable employment).

I'm doing 30hrs/week jobs for more than a decade now. In my experience you will not find a niche in the industry where part-time jobs are waiting for you to grab one. Instead, you will have to carve such a job out of the common job market. That's not easy, because many only bargain for money when they interview, so companies are not used to employers wanting to work less, but it's not impossible.
I have found the following important when looking for a part-time job:

Be good at what you do. When you are good, they will want you, and are prepared to pay for it. Some candidates will want more money, some will want more holidays, a few will want fewer working hours.
In an interview, explicitly ask about a company's overtime policy. Is overtime something normal at the shop, that's done by everyone regularly? Unpaid? If so, you will be unlikely to really be working less than 40hrs, no matter what contract you sign.
If you have the feeling they might be hard to convince to let you work 30hrs, start out offering less (20hrs?) and then let yourself be "persuaded" to work 30hrs. :) I did this with my first part-time job.
Don't expect too much pay or other benefits when you first do this. Under these conditions you are closer to a junior job than you used to be. Once you can show excellent references for two or three such jobs over the last decade it will be easier to convince employers that your special needs are worth the hassle.

Once you have such a job, be sure to follow these rules:

I usually explain upfront, right in the interview, that I am never working for free. I clock every hour I work for the company, and certainly clock overtimes I put in, and I expect to take leave the same amount of hours for compensation. (I have, twice over more than a decade, accepted money instead. But that was me accepting it, rather than them pressing me to do it.)
Do not let them press you into doing more hours without compensation. You might have relinquished other benefits (like money) for doing 30hrs/week. There is no point in relinquishing what you got for that. (The others wouldn't give up that money even if pressed hard, right?)
Remind everyone that you only have 75% of the time others have. Make sure that your team leader, when planning resources, remembers that. If they have never worked with such an employee, then this will need constant reminding in the beginning.
We all know that in this industry crunch time is a common phenomena. When others work overtime, you might have to do that, too. However, be sure to make it absolutely clear that for you, 40hrs/week already is overtime.

