The Azure SQL Database service triggers an automatic failover after a failure is detected and the grace period has expired. What is the grace period? You can find this setting when building a failover group.

If memory serves me correctly, this used to be only 24 hours, but now we can set a minimum of 1 hour. What does it mean? Lets assume I set this to 24 hours, I got clarification from Microsoft a while ago and they stated:

“When the R/W grace period set to 24 hrs, it means that if the outage get mitigated by Azure in <24 hrs, the failover will not be triggered at all and therefore no data will be lost. But the flip side of it is that the application will be down for 24 hrs”..