AZ-900 Cheat Sheet: 7 Terms You MUST Know

The AZ-900 exam loves vocabulary.

You will see questions asking you to pick the right word for a specific scenario. If you mix up "Scalability" with "High Availability," you lose easy points.

Here are 7 critical terms explained with simple analogies so you never forget them.

1. Scalability (Growing Pains)

Scalability is the ability of your system to handle more users without crashing. There are two ways to do this:

Vertical Scaling ("Scale Up") 🏋️‍♂️

  • Definition: Adding more power (RAM/CPU) to an existing server.
  • Analogy: Like a bodybuilder getting stronger muscles. There is a limit—eventually, you can't get any bigger.
  • Pro: Easy to do. Con: Requires a restart (downtime).

Horizontal Scaling ("Scale Out") 🐜🐜

  • Definition: Adding more servers to work together.
  • Analogy: Like an army of ants. One ant is weak, but 1,000 ants can move a mountain. If you need more power, just add more ants.
  • Pro: Unlimited growth and no downtime. Con: App must be designed to support it.

2. Staying Alive: HA vs. Reliability

These two sound similar, but the exam treats them differently.

High Availability (HA) ⏱️

  • Focus: Keeping the service running with minimal downtime.
  • The Goal: "The shop is open 99.9% of the time."
  • How: Using clusters or Availability Zones so if one server fails, another takes over instantly.

Reliability 🛡️

  • Focus: The system's ability to recover from failures and continue functioning correctly.
  • The Goal: "If the shop burns down, we can rebuild it quickly and not lose any orders."
  • How: Backups, Disaster Recovery, and Site Recovery.

3. Predictability (No Surprises)

The cloud lets you predict the future in two ways:

  • Performance Predictability: You know your app will run fast, even if 10,000 users log in at once (thanks to Auto-scaling).
  • Cost Predictability: You can use tools like the Pricing Calculator to know exactly how much your bill will be before you spend a dime.

Bonus: The Hybrid Heroes

These tools help you mix on-premise servers with the cloud.

Azure Arc (The Universal Remote) 🎮

Imagine you have servers in AWS, Google Cloud, and your own basement. Azure Arc lets you manage ALL of them from the Azure Dashboard. It extends Azure management to any infrastructure.

Azure VMware Solution (The Easy Mover) 📦

Many companies use VMware to run their private servers. This service lets you move those VMware machines directly into Azure without changing them. It’s like moving houses without having to unpack your boxes.

Exam Tip: Memorize the difference between Vertical (Scale Up) and Horizontal (Scale Out). That is a guaranteed question!

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