It seems there was a problem with Heroku from 5/9/2018 to 13/9/2018 with their eu hobby dev databases. Their internal tools had a connection leak that opened connections with appname `yobuku` and with another appname called `puma cluster worker`.
The only out was to manually kill these connections every few hours.
The problem seems to be resolved now.

It seems there was a problem with Heroku from 5/9/2018 to 13/9/2018 with their eu hobby dev databases. Their internal tools had a connection leak that opened connections with appname `yobuku` and with another appname called `puma cluster worker`.
The only out was to manually kill these connections every few hours.
The problem seems to be resolved now.