Hello Melanie, we ran a debugging session, downgraded almost all dpkg's and finally figure out it is jsonschema lib causing the performance issue. The change seems to be introduced in https://review.opendev.org/c/openstack/nova/+/850021 we got rid of the latency after downgraded to 3.2.0-0ubuntu2, though apt is not accepting the version since >4.0 is required by nova, we used some hacky way to ignore it. When I was looking at the commits to force require jsonschema >4.0, seems the main purpose is to remove the unit test. Just want to raise the concern that the certain version of it could cause latency, and we haven't looked into the history of the library to figure out what change exactly did that. We either did not try to pull some newer version of it to see if it's already resolved. Hope this could help and if you have any suggestions or concern please let me know. Thanks. Best, Chang