How did engineers make Facebook Messenger more efficient?

As Facebook unbundled messaging from the main mobile app, the company started making major improvements to its standalone Facebook Messenger app. A blog post by Facebook engineers Jeremy Fein and Jason Jenks shows how the social network made Messenger more efficient.

Fein and Jenks wrote that Messenger has decreased non-media data usage by 40 percent (developing a new service called Iris to power it). Users have taken note of improvements to Messenger, as there has been a 20 percent dip in the number of people who experience errors when trying to send a message.

Fein and Jenks wrote of what it took to revamp the Facebook Messenger app:

Messaging data has traditionally been stored on spinning disks.