Whenever we need to notify a user of something happening on our platform, whether it’s a personal push notification from one user to another, a new Dub, or a notification going out to millions of users at the same time that new content is available, we rely on AWS Lambda to do this task for us. When we started implementing this feature 2 years ago we were luckily able to get early access to the Lambda Beta and are still happy with the way things are running on there, especially given all the easy to set up integrations with other AWS services.
Lambda enables us to quickly send out million of pushes within a couple of minutes by acting as a multiplexer in front of Amazon SNS. We simply call a first Lambda function with a batch of up to 300 push notifications to be sent, which then calls a subsequent Lambda function with 20 pushes each, which then does the call to SNS to actually send out the push notifications.
This multi-tier process of sending push notifications enables us to quickly adjust our sending volume while keeping costs & maintenance overhead, on our side, to a bare minimum.