On Jira Server, the search queries are executed in the same Java Virtual Machine (JVM) as Jira. On a cloud hosting, the JQL Search Extensions service is a separate deployment communicating with Jira over the REST API. As a result, all operations in Jira Cloud are indexed asynchronously, and any changes in Jira are reflected in the JQL with a slight delay.
Filters are indexed periodically. You can run a manual sync for any of your saved Extended Search filters to prioritize syncing and ensure your most critical filters are up to date. See Extended Search filters to learn more about filter limitations.