This actually has nothing to do with who is online or if the app is currently requesting info. An example:
You have a posts db table (or collection in the case of Parse, since they're using MongoDB) and a user_posts table. The user_posts table contains references to the posts to show in each user's personalized feed (fan out model). When a post is created, the app needs to perform x inserts into user_posts, where x is the number of users who's feed will include this post. EACH insert counts as a request in Parse, so if a user with 100 followers posts something that needs to be distributed to the 100 follower feeds, that'll require 100 requests/second.
Comments
This actually has nothing to do with who is online or if the app is currently requesting info. An example:
You have a posts db table (or collection in the case of Parse, since they're using MongoDB) and a user_posts table. The user_posts table contains references to the posts to show in each user's personalized feed (fan out model). When a post is created, the app needs to perform x inserts into user_posts, where x is the number of users who's feed will include this post. EACH insert counts as a request in Parse, so if a user with 100 followers posts something that needs to be distributed to the 100 follower feeds, that'll require 100 requests/second.