If you want to have highly available Azure SQL Database it is highly recommended that you configure Active Geo-Replication (this feature is available for all databases in all service tiers). Active Geo-Replication consists of two (or more) databases in different regions, where one database is primary (read + write operations) and all other databases are secondaries (allowed only read operations). Secondary databases are automatically synced with changes in your primary database.

If you are using Azure SQL Database you may occasionally experience following exception (this is example throw by native SqlClient library): System.Data.SqlClient.SqlException: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. This failure occurred while attempting to connect to the routing destination. What is this? Azure system may occasionally quickly shift hardware resources to better load-balance various workloads. During this reconfiguration time span, you may have connectivity issues to Azure SQL Database.