Azure SQL Database is a fully managed platform-as-a-service (PaaS) database offering that runs on the latest version of the SQL Server database engine, enabling highly available and performant database instances without hardware upgrades or maintenance. It supports both relational and non-relational data models, allowing for consolidation and management of different data formats in a single database instance. Azure provides various purchase models and service tiers to support different workloads, including database transaction units (DTUs) and virtual cores (vCores), which dictate resource limits and costs. Monitoring Azure SQL databases helps manage costs and detect performance issues, with telemetry data including metrics on resource utilization, deadlocks, and audit logs. Key performance metrics include compute, storage, worker usage, and limits, as well as connectivity metrics such as active connections to a database. The platform provides features like threat detection alerts, auditing, and logging to protect databases from security threats and ensure compliance with regulatory requirements. By monitoring key metrics and logs, users can gain better visibility into their Azure SQL databases' health and performance, enabling data-driven decision-making to optimize costs and improve application reliability.