Understanding Azure SLAs: What 99.9% Really Means

When you start using Microsoft Azure, one of the first things you’ll come across is the concept of a Service Level Agreement, or SLA. It sounds straightforward — a promise of reliability from Microsoft — but the details can be confusing. You’ll see numbers like 99.9%, 99.95%, or even 99.99% uptime, and it’s easy to assume they all mean near-perfect reliability.

But what does “99.9%” actually mean in real-world terms? How much downtime does it allow? And how should you plan your architecture to meet or even exceed those targets? Let’s break it down in plain English.

 

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