GET /api/authz/v1/assignments/ is slow due to too many queries on PolicyCacheControl

[mariajgrimaldi]

Description

A trace on muscat-openedx | LMS (Mon Mar 21, 2026) showed a 28-second response time on GET /api/authz/v1/assignments/?page=1&page_size=10&search=user_.

Time breakdown: 94% view, 5% SQL, 1% other. The SQL portion consisted of 1,339 calls to openedx_authz_policycachecontrol, all reading the same row:

SELECT `openedx_authz_policycachecontrol`.`id`, `openedx_authz_policycachecontrol`.`version`
FROM `openedx_authz_policycachecontrol`
WHERE `openedx_authz_policycachecontrol`.`id` = %s LIMIT 21

ScoutAPM flagged this as an N+1 pattern and estimated 1,610ms in potential savings.

[MaferMazu]

@mariajgrimaldi, if your findings require you to address this with a simple fix (to avoid adding complexity to something we need to backport) and to open a separate issue for a long-term solution, please do so.