Truthfully the billing system is one of the most fascinating parts of our stack to me. Twilio's utility pricing model generates an incredible volume of minute

Truthfully the billing system is one of the most fascinating parts of our stack to me. Twilio's utility pricing model generates an incredible volume of minute transactions, which is a fascinating engineering problem to solve at scale. That solution ultimately came up short last week, but think the foresight behind a number of the features (double bookkeeping to an unrelated, persistent datastore in particular) aided in recovery.