[SPIKE] Investigate on improving SubscriptionController#create response time

According to the kibana query below, we see that the endpoint: SubscriptionsController#create has the worst Appdex, with 515 operations over the threshold out of 674.

This issue is a placeholder to dig deeper into the request and try to find a way to improve the response time.

  1. Rails Requests Apdex: slow requests exceeding the threshold along with total number of request

Screenshot_2022-10-05_at_17.57.45

Kibana log

  1. Rails slow requests: Top slow requests

Screenshot_2022-10-05_at_18.09.53

Kibana log

Edited by Bishwa Hang Rai