SQL in the Cloud: Azure SQL

Managing physical servers is expensive. Azure SQL Database provides a fully managed "Platform as a Service" (PaaS) version of SQL Server. Microsoft handles the patching, backups, and high availability, allowing you to focus on your code.

1. Serverless vs Provisioned

• Provisioned: You pay for a fixed amount of CPU and RAM (e.g., 2 vCores). Good for predictable workloads.
• Serverless: The database "Sleeps" when not in use and auto-scales up during traffic bursts. You only pay for the seconds it was running. Perfect for Dev/Test and small apps.

2. High Availability (Built-in)

In Azure, your data is automatically replicated 3 times within a datacenter. If a hardware node fails, Azure flips a switch and you are back online in seconds with **Zero Data Loss**. You don't need a DBA to set up complex 'Failover Clusters' anymore.

4. Interview Mastery

Q: "What are the main differences between Azure SQL Database and SQL Server on a VM?"

Architect Answer: "Azure SQL (PaaS) is 'Database-as-a-service'; you don't have access to the OS or the SQL Instance settings (like Master DB or SQL Agent). It is cheaper and easier to scale. SQL Server on a VM (IaaS) is a full server; you have 100% control, but you are responsible for patching the OS and managing backups. We choose PaaS for new cloud-native apps and VM (IaaS) for legacy migrations that require 100% instance-level compatibility."