Design a highly available Azure SQL database that must (1) fail over between replicas with no data loss, (2) remain available during a zone outage, and (3) minimize cost. Which deployment option should you choose?

Azure SQL Database Business Critical is the correct choice. It uses Always On availability groups with multiple replicas, ensuring no data loss during failover by committing transactions to at least three replicas before acknowledging the commit. Its zone-redundant configuration distributes these replicas across different availability zones, maintaining availability during a zone outage. While Managed Instance Business Critical also meets the availability and data loss requirements, it is generally more expensive due to its dedicated instance nature. Basic and Standard tiers do not offer zone redundancy or the same level of immediate data loss protection as Business Critical.