# Azure SLAs

**1. What is an SLA?**

A **Service Level Agreement (SLA)** in Azure defines the **uptime and performance guarantees** provided by Microsoft for a specific service. If the SLA is not met, customers may receive **service credits** as compensation.

### **2. Azure SLA Plans**

🔹 **Subscription-Based SLAs** – Higher-tier plans offer better guarantees.\
🔹 **No SLA for Free Plans & Preview Services** – These services are not covered by availability guarantees.

### **3. Service Credits**

If an Azure service fails to meet its **uptime commitment**, customers can request **service credits** based on the downtime percentage.

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### **4. Azure Composite SLA**

A **Composite SLA** is the combined reliability of multiple dependent services. It is calculated by multiplying the SLAs of individual services.

🔹 **Adding More Services Lowers SLA** – The overall reliability decreases as more dependent services are added.\
🔹 **Adding Redundancy Improves SLA** – Deploying services across **multiple zones/regions** increases availability.\
🔹 **Zonal & Regional Redundancy** – Services with built-in **geo-replication** have higher SLAs.\
🔹 **Different SKUs & Service Tiers** – Premium tiers offer **better uptime guarantees** than basic ones.

#### **Example: Composite SLA Calculation**

{% code overflow="wrap" %}
```
VM SLA = 99.9%
Storage SLA = 99.99%
Then, the Composite SLA = 99.9% × 99.99% = 99.89% (lower than the individual SLAs).
```
{% endcode %}
