It seems to me that a smaller app would be more likely to occasionally burst over 30 req/s than go over 1m req/mo. Is it as simple as retrying requests that return error code 155 (per the FAQ)?
I've been using Parse for a few years now and have always been happy with them. Their service offerings have been growing right along with my needs so it's been great. I'm happily welcoming this announcement.
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.
I've made an native iOS app to use the Data Browser from the phone. It's something I think a lot of Parse users can benefit from using, I wish they'd informed about it in their presentation!