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  • Giovanni Maria Casucci thinks this is interesting:

These replicas are offline, but they can be brought online for an application to fail-over to them in the event of a datacenter disruption. Active geo-replication (available to Premium-tier users) provides the most rapid recovery time by keeping four geo-replicated live secondaries.

From

Cover of Exam Ref 70-534 Architecting Microsoft Azure Solutions

Note

should be also be available to standard tier (not only premium)