I have the same problem.
I startet testing the API via curl and recognized that the first API calls ran fast. After a while it got slow. I tested for example creating and deleting of a user. Everytime with the same credentials.
We have <10 users!
So i thought it’s kind of a database cleanup problem but occ files:cleanup and occ versions:cleanup didn’t improve the long time.
We have a similar stack like @nutomic:
- Nextcloud version 18.0.4 (<10 users)
- OS: debian 10.3
- webserver nginx 1.14.2
- PHP version: PHP 7.3.17
UPDATE:
I took a look under the preferences --> overview and there was a warning of missing indices.
So i made a occ db:add-missing-indices and after that it was a way much faster! Hope it helps.