Currently there is no limit to how much a user can write to the db in a given amount of time. This leaves it vulnerable to something such as a script to add to the database repeatedly until it used all available bandwidth on the Firestore db (Lookin' at you, A). Not really sure the best solution to this. Fixing Issue #1 will drastically increase how many todos the user can add before the Firestore db exceeds it's bandwidth (since it was caused by the read query after every add), but adding something to limit the number of pending todos, even to something like 100, would decrease the risk of something like this.
Currently there is no limit to how much a user can write to the db in a given amount of time. This leaves it vulnerable to something such as a script to add to the database repeatedly until it used all available bandwidth on the Firestore db (Lookin' at you, A). Not really sure the best solution to this. Fixing Issue #1 will drastically increase how many todos the user can add before the Firestore db exceeds it's bandwidth (since it was caused by the read query after every add), but adding something to limit the number of pending todos, even to something like 100, would decrease the risk of something like this.