The worst part is not the missing JOIN. This happens, especially with juniors.
It's the 'all signup errors warranted paging the on-call even on 4am' bureaucratic decision followed by being unable to apply any fix quickly. No surprise the author did not stay.
The worst part is more senior devs being happy to watch it happen and even accept the commits, and then write a long winded story of how this 'car crash unfolded' apparently unaware that they're a tacitly active contributor to it happening and then escalating out of control.
If you're going to be aper of throwing junior devs under the bus, at least have the self awareness not to brag about it on the itnernet.
It's the 'all signup errors warranted paging the on-call even on 4am' bureaucratic decision followed by being unable to apply any fix quickly. No surprise the author did not stay.