Safe releases: flags, remote config and kill switches
Essence
A mobile release can't be rolled back: the build is already on devices, and a fix has to pass review and reach users, which takes time. So release safety is built in advance: new functionality ships turned off, is enabled gradually and can be turned off remotely within minutes.
The rest of this answer, with code and interview follow-ups, is in the DevPrep app.
Read the full answer in DevPrep