Hello, We have recently encountered a situation where the response time for the openstack server list command is significantly slower when specifying os-compute-api-version 2.96 for certain projects. In comparison with version 2.95, some projects experience a response time that is 2-3 times longer, while other projects show little to no difference. We understand that in version 2.96, there was a change to obtain the availability zone from the request_spec [1]. However, upon checking the instance records in request_spec for the projects, we have not identified any differences that would account for this slow response behavior. Additionally, we have observed that when certain ERROR VM is present, the response time for the server list can become considerably slower for specific projects. In one case, we resolved the slow response issue by deleting instances that did not have corresponding fault records in the database. However, the exact reason why this action resolved the issue remains unclear. If anyone has more detailed information or potential solutions regarding these issues, or if you have encountered similar situations, we would greatly appreciate your insights. [1] https://git.linecorp.com/Flava-IaaS/nova/commit/c98c8d84eec6e65f1b67ae1ab827... Best regards, Masanori Kuroha