Notification System: Topics and Priorities

At 09:00 the bank releases its largest campaign, an offer to 4 million customers. At 09:04:10 the card system holds a payment of 640 dollars and creates a fraud check for the account owner. The same campaign and the same fraud check pass through two designs that differ in one decision: how messages are divided into topics.

In the first design, there is one topic per channel. The router writes the campaign's 2.4 million push messages into the push topic at 9,600 a second, and the push senders send at most 3,000 a second, the provider's limit. By 09:04:10, 2