Basically my question boils down to are they constantly growing and need staff, or is it a rough place to work at and they have lots of turnover? I'm interested in applying but kind of want to know more.
One answer might simply be because they can. YC companies are the only ones allowed to advertise job postings by post instead of once a month in the thread and some are more diligent about using this benefit than others. Doesn’t necessarily say much about the dev position as it does about the person in charge of HR.
You'll find this pattern with some YC companies. I recall DrChrono was like this for several years with the constant HN job listings for a DevOps engineer.
In my eyes, it's a red flag and not a great sign. If a company treats people fairly and pays market rates, the job listing is unlikely to stay open very long.
At the same time, a red flag is just that - a signal, not damning proof of anything untoward.
Some recruiter, I don't know if directly affiliated, really wanted me to apply there. She said my resume didn't say REST API enough, and that I should add every rest project there.
I modified it to add REST API no less than 15 times, almost sarcastically. She was super pumped with it now.