Azure SQL Database is a fully managed relational database service from Microsoft, built on the SQL Server engine and running on Microsoft Azure. According to the vendor, Microsoft handles patching, backups, availability and monitoring. The service offers, among other things, the Hyperscale tier, serverless compute, elastic pools, built-in JSON support and vector search for AI applications. Availability can be increased with zone redundancy inside an Azure region.
Microsoft Corporation is a US company, so the service falls under US jurisdiction, including the CLOUD Act. For Azure, Microsoft has documented the EU Data Boundary: when a customer deploys in an EU Data Boundary region, customer data and pseudonymised personal data are stored and processed in datacenters in the EU and EFTA, with limited documented exceptions. Microsoft publishes a Data Protection Addendum for its products. Azure SQL Database is proprietary and not open source.