Posting a comment too long

[cysjonathan]

Issue

Posting a comment takes ~5s to complete.

Expected behaviour

Gold standard should have server respond in <100ms.

[cysjonathan]

Slow commenting issue seems sporadic even when testing on staging (ranges between 300ms to 20s on staging), and requires further investigation.

Additionally, query on /courses/<course-id>/comments pages are slow > few seconds (might need to find a course with large number of comments).
Query for comments under My Students can take up to minutes.