Get bulk permissions\https://developer.atlassian.com/cloud/jira/platform/rest/v3/api-group-permissions/#api-rest-api-3-permissions-check-post API endpoint currently performs a lookup in all the users in the site. The accountID query parameter only acts as a filter.

This is an expensive operation; especially for large sites with 500K+ users.
Please add an API endpoint that can be used to search a specific set of users (either by groups or array of accountIds).