Ok - I've now tried with 8 workers instead of 4 and its the same. I should note that the apiserver container CPU usage is pretty low (~5-10% ). Also memory-wise it looks pretty in-spec to me. Below is a typical docker stats output when the server is behaving pretty sluggish
CONTAINER ID NAME CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O PIDS 5e9160ba93d7 clearml-webserver 0.00% 5.996MiB / 7.446GiB 0.08% 803kB / 777kB 0B / 0B 6 e1596def9c4b clearml-apiserver 0.33% 429.7MiB / 7.446GiB 5.64% 50.9MB / 20.5MB 0B / 0B 82 7664869a2ab5 clearml-elastic 0.14% 3.524GiB / 7.446GiB 47.33% 2.21MB / 2.55MB 0B / 0B 85 67476e6b48d6 clearml-fileserver 0.01% 25.21MiB / 7.446GiB 0.33% 18.8kB / 0B 0B / 0B 2 a95f2a7f07e6 clearml-redis 0.06% 2.504MiB / 7.446GiB 0.03% 133kB / 51kB 0B / 0B 4 41d9155c7fa3 clearml-mongo 0.13% 997.1MiB / 7.446GiB 13.08% 4.62MB / 37.3MB 0B / 0B 55