Data resilience at Fastmail comes down to a principle our CEO, Bron Gondwana, wrote down over ten years ago. The primary copy is gold. Back it up, replicate it. Principles rarely change, and that one has not.
In April it got tested. A bug wiped mailboxes for 8 accounts. Backups brought all of it back, down to 5 sent emails recovered from temporary files inside Cyrus. The write-up covers what broke, PR numbers and all.
