Azure Relational Database Selection

Choosing the right Azure relational database requires evaluating several factors together rather than in isolation. Workload patterns determine the deployment model: single databases suit independent applications, elastic pools suit multi-tenant applications with variable usage, and hyperscale suits large-scale workloads with high throughput requirements. All services provide ACID compliance for consistency, but the specific isolation levels and locking behavior differ between SQL Server, PostgreSQL, and MySQL, so applications depending on database-specific concurrency behavior may need to stay with their native platform. High-availability architectures differ in recovery time and data loss tolerance: zone-redundant deployments protect against datacenter failures within a region, while geo-replication protects against regional disasters but introduces some replication delay. Scalability options include vertical scaling (increasing compute and storage) and horizontal scaling (adding read replicas), but only Azure SQL Database's hyperscale tier separates compute from storage for near-instant scaling. Cost considerations should account for compute, storage, backup storage, and data egress charges, with reserved capacity or hybrid benefit options reducing costs for predictable workloads.