Azure SQL and Cosmos DB

Azure offers a comprehensive range of database services. This lesson focuses on the two most important: Azure SQL Database for relational workloads and Azure Cosmos DB for globally distributed NoSQL workloads.

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Azure SQL Database

Azure SQL Database is a fully managed relational database service based on the Microsoft SQL Server engine. It handles patching, backups, monitoring, and high availability so you can focus on your application.

Deployment Options

Option	Description
Single Database	A standalone database with its own resources
Elastic Pool	Multiple databases sharing a pool of resources (cost-effective for variable workloads)
SQL Managed Instance	Near-100% compatibility with on-premises SQL Server (for lift-and-shift)

Purchasing Models

Model	Description
vCore	Choose the number of virtual cores, memory, and storage independently. Best for existing SQL Server users (Azure Hybrid Benefit applies).
DTU	Bundled measure of compute, storage, and I/O. Simpler pricing for predictable workloads.

Service Tiers

Tier	Best For
General Purpose	Most workloads. Balanced compute and storage.
Business Critical	Low-latency, high-IOPS workloads. Built-in read replicas.
Hyperscale	Very large databases (up to 100 TB). Rapid scale-out.

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Key Features

Automatic Backups

• Full backup weekly, differential every 12–24 hours, transaction log every 5–10 minutes
• Point-in-time restore within the retention period (7–35 days)
• Long-term retention (up to 10 years) for compliance

High Availability

Azure SQL Database has built-in high availability (99.99% SLA):

• Data is replicated within the data centre
• Zone-redundant option replicates across availability zones (99.995% SLA)
• Automatic failover — no action needed from you

Security

• Transparent Data Encryption (TDE) — encrypts data at rest (enabled by default)
• Always Encrypted — client-side encryption for sensitive columns
• Advanced Threat Protection — detects anomalous database activities
• Entra ID authentication — use Azure identities instead of SQL logins
• Firewall rules and Private Endpoints — restrict network access

Intelligent Performance

• Automatic tuning — applies tuning recommendations (index creation, query plan correction)
• Query Performance Insight — identifies top resource-consuming queries
• Intelligent Insights — AI-powered diagnostics

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Azure Cosmos DB

Azure Cosmos DB is a globally distributed, multi-model NoSQL database designed for massive scale, low latency, and high availability.

Key Differentiators

Feature	Detail
Global distribution	Replicate data to any number of Azure regions with a few clicks
Single-digit millisecond latency	Guaranteed < 10ms reads and writes at the 99th percentile
99.999% availability	With multi-region writes enabled
Elastic scale	Throughput and storage scale independently and automatically
Multi-model	Supports multiple APIs and data models

Supported APIs