Discovery Service - Refreshing the ElasticSearch Documents

I solicit help from folks who have worked on the Discovery Service APIs!

I have installed Kibana to visualize the underlying ElasticSearch documents.

It is not entirely clear to me if relevant changes to the configuration data (metadata) in Discovery Django Admin interface automatically gets synced with ElasticSearch…

Here are my observations:

  1. Adding new courses etc. in CMS and then running refresh_course_metadata and update_index instantaneously updates elasticsearch documents (and Discovery Admin interface as well).

  2. However, adding metadata in Discovery Admin interface (creating subjects, Associating Subjects with Courses, associating authoring_organizations with courses etc.) do not reflect instantaneously in elasticsearch. I even tried running ‘refresh_course_metadata’ and ‘update_index’ to no avail. However, after several hours, I saw these information synced to elasticsearch.
    Question:
    So, what is the underlying system/logic for Discovery->to->elasticsearch sync?
    a) is it some hourly job?
    b) is refresh_course_metadata step mandatory for this scenario?

Thanks.