502 Bad Gateway for only two Topics

Yes, it is an ARM CPU. I accidentially inquired further and found that when I open a 502 page, I see this process spiking:

unicorn worker[1] -E production -c config/unicorn.conf.rb

99.0 is the cpu percentage:
image

And this also stays up several seconds after a 502 page is returned to the browser. What is it doing?

How can I check this?

Hm. These are the minimal requirements. Also, the RAM never spikes up or even seems to move.