After days of sitting, coding, my back aches like f*ck. How do you guys handle this?

You're sitting wrong my friend. To properly fix something, never break it in the first place. Go to Ikea and get a chair compatible with your back architecture. You'll know it when you find it - as with all matters of the butt.

Comfy chair, good posture.

Masturbation, mostly.

Just a small pillow at your lumbars and a box under your foot if needed (actually I use a shoes box consolidated with tape)

I've got a footrest ergonomic chair and a microwave beanie that sits on my neck :)

Try to save some money for aeron chair.

Good posture, chair, mattress and screen's height and distance.

Sit up straight 😄

Er, we don't code for days on end, we take breaks, have a bit of a life. Quality code requires occasional distractions and disconnections.

I am good for 4, maybe 6 hours, after that my code is indistinguishable from drunk code. Nice 90/120 min break, go for a run, walk the dog, take care of the little one and life's good again.

Yoga for back pain

Stand up desk.