So the PostgreSQL server was under really high load whenever the web worker was running, which affected all of the instance.
The solution was on the PostgreSQL side: https://pgtune.leopard.in.ua
I don't know which parameter was important, but it's day and night
(Thanks a lot to Jackster on the Discord server)
@angristan there is a mstdn.io Discord ?
@Matthieu Mastodon discord
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