I know someone who worked full time from home with no formal childcare from 3 months. She said returning to work by 3 months is normal in her country, and she felt lucky she could work from home with baby rather than using a nursery.
Her hours were flexible so she worked when baby napped and when her husband was there in the evenings and at weekends.
When baby was older, twice a week a babysitter took her baby out for a walk to the playground, I think for a couple of hours. They didn't use a nursery until baby was one, I think due to finances.
Her baby was exceptionally calm and easygoing - slept predictably by being put in the cot with a song.
Being routine focused and expecting baby to settle to sleep alone (and tolerating
some crying to achieve this) was the norm in her country, as was expecting baby to just need one predictable overnight feed by three months. She also fully formula fed as breastfeeding didn't work out (although the advice she received from relatives and doctors in her country would have made breastfeeding harder to work eg not feeding on demand).
She said she was happy with the situation and it enabled her to carry on her very interesting career. She did say she didn't have many opportunities to make friends with other mums or take baby to playgroups.
She was well rested as baby only walking once at night, her husband was happy to do lots of baby care in the evenings (when babies often grumpy) and weekends so she could rest, her baby was on a clockwork schedule and seemed a cheerful happy baby.
I would say the rest of us were AMAZED this was even possible.