It's an edge case.

It's an edge case of an edge case.

But you'd think they'd do something like '200 users have liked...' A cron like every 5 minutes (or more) after the first 10 likes or something like that..

The problem with these systems is that batching would make the implementation more complex. Sending say 10m notifications per second in a fire-and-forget manner is easily distributable en requires little state. Batching per user would be do-able but requires thinking about distribution (messages to the same user should at some point go over the same machine) and tracking a bit of in-memory state per user.

In short I can imagine the trade-off of less-optimal support for some edge cases like these.

Yeah but then is it really notification worthy? If you're that popular, you just post, and then check back in a while to see how it did. There's nothing really "notification worthy" like when it's more like 1-to-1 communication.

It seems like most instragram users have over 100 followers[1], if they're all active and connected that means a sizable chunk of likes (or whatever else you can do) when you post something.

Surely sending all these notifications isn't entirely free - someone else posted Snowden receiving 47 gigs of mail because of email notifications.

You could do something like send notifications with some sort of back-off. Send them for 10 seconds, then back off to a minute's worth chunk, then 10 minutes, then an hour.

Then again, I don't have any statistics on how much these external services actually cost, nor how often this actually does happen. Simplest thing is for instagram/twitter to not care, and to point the finger at apple/android and tell them they should have UI to squelch high-frequency notifications.

[1] http://www.statista.com/statistics/419326/us-teen-instagram-...

> It seems like most instragram users have over 100 followers[1], if they're all active and connected that means a sizable chunk of likes (or whatever else you can do) when you post something.

Bad assumption, given the 90:9:1 rule (99% lurk while 1% participate)

https://en.wikipedia.org/wiki/1%25_rule_(Internet_culture)

1% does mean a lot when you have millions of followers, though.