To be clear, Twitter runs Aurora which is open source and has proven itself to be stable, battle-tested, and scalable; development on Aurora began in 2010, and over the years Mesos and Aurora have evolved together. Aurora has cron capabilities built into it, and Twitter does not run Marathon or Chronos.

Twitter engineering recently blogged about Aurora with a bit more on its history: https://blog.twitter.com/2015/all-about-apache-aurora, and The New Stack recently published a two-part article on the project: http://thenewstack.io/twitters-aurora-relates-googles-borg-p..., http://thenewstack.io/twitters-aurora-replaces-operating-sys...

(full disclosure, I work at the tweet shop)