Azure Fundamentals (AZ-900) Q&A

Cloud Models & Concepts

Q: What’s the difference between scalability and elasticity? A:

Scalability: Ability to grow over time (add more VMs)
Elasticity: Automatically respond to demand (add/remove VMs instantly)
Example: Your app grows from 1M to 10M users = scalability. It handles traffic spikes at noon = elasticity.

Q: Which cloud model gives you the MOST control? A: Private Cloud (you own everything). Public cloud gives LEAST control.

Q: When would you use a hybrid cloud? A: When you need:

Some data on-premises (compliance)
Some in public cloud (scalability)
Example: Store patient data locally (HIPAA), use Azure for analytics

Q: Is cloud computing expensive? A: Depends:

Upfront: No hardware costs (good)
Monthly: Can be high if over-provisioned (bad)
Solution: Right-size resources, use reserved instances

Service Models (IaaS/PaaS/SaaS)

Q: I need an OS I can control. Which service model? A: IaaS (you manage OS, apps, data). Example: Azure VM.

Q: I don’t want to manage the OS. A: PaaS (provider manages OS). Example: App Service.

Q: I just want to use the app. A: SaaS (provider manages everything). Example: Office 365.

Q: Who manages security patches for VMs? A: You (partly). VM OS = you. Hypervisor = Microsoft.

Q: Can I run containers on App Service? A: Yes, but it’s still PaaS. App Service can host Docker containers.

Azure Services

Q: When would you use Blob Storage vs File Shares? A:

Blob: Large files, images, videos, archives
File Shares: Network shares (like SMB), shared folders
Example: Video library = Blob. Shared folder for documents = File Share.

Q: What’s the difference between Azure SQL Database and SQL Server on VM? A:

SQL Database: PaaS (Microsoft manages patches, backups, HA)
SQL Server on VM: IaaS (you manage everything)
Best practice: Use SQL Database (less work)

Q: When would you use Cosmos DB instead of SQL? A: When you need:

Global distribution (data in multiple regions)
NoSQL (flexible schema)
High throughput (millions of reads/sec)
Example: Mobile app with users worldwide

Q: What’s Azure Functions used for? A: Event-driven, serverless compute. Examples:

Process image when uploaded to blob
Send email when database changes
Run scheduled job at midnight
Handle webhook from external service

Q: How is Functions cheaper than VMs? A: You only pay for execution time (not idle time). VM runs 24/7 = always paying.

Pricing & Costs

Q: Why is data transfer out so expensive? A:

Infrastructure cost (limited bandwidth)
Cloud providers charge to recoup costs
Solution: Use CDN, ExpressRoute, or keep data internal

Q: What’s the difference between reserved instances and spot VMs? A:

Reserved: Commit 1-3 years, 30-72% discount, won’t be evicted
Spot: Up to 90% discount, can be kicked off anytime
Best for spot: Batch jobs, fault-tolerant apps

Q: Free account limits? A:

$200 credit for first month
Free services for 12 months (then pay)
Some always free (limited): Functions, Cognitive Services

Q: Does Azure charge for failed transactions? A: Yes, some services charge per operation (read/write/delete). Failed requests still count.

Security & Compliance

Q: Who’s responsible for security? A: Both (shared responsibility):

Microsoft: Infrastructure, physical, hypervisor
You: OS, apps, data, user access, encryption

Q: Does Azure encrypt data by default? A: Yes (at rest, in storage). But:

Not by default: VM disks (you can enable)
Not included: App-level encryption (you must do)

Q: What’s the difference between a role and a permission? A:

Role: Container of permissions (Owner, Contributor, Reader)
Permission: Specific action (read VM, delete storage)

Q: Can I restrict a user to one resource? A: Yes, assign role at that resource level (not subscription).

Q: What happens if I delete a resource group? A: Everything inside is deleted (VMs, databases, storage). Be careful!

Availability & Disaster Recovery

Q: What does 99.95% SLA mean? A: System is down maximum 22 minutes/month.

Q: How do I get 99.95% SLA? A: Deploy 2+ instances across availability zones or availability sets.

Q: What’s the difference between RTO and RPO? A:

RTO: How quickly you recover (time objective)
RPO: How much data you can lose (point objective)
Example: RTO=1 hour, RPO=5 minutes (lose at most 5 mins of data)

Q: Do I need disaster recovery? A: Depends on business impact:

Critical system: Yes (massive cost)
Development: No
Business-critical: Probably

Networking

Q: What’s a virtual network (VNet)? A: Isolated network in Azure (like private network). You define:

IP address range (10.0.0.0/16)
Subnets
Routing, DNS, security

Q: Can VNets in different regions talk to each other? A: Yes, via:

Peering: Fast, low latency, same Azure backbone
VPN: Over internet, slower
ExpressRoute: Dedicated private link, fastest

Q: What’s an NSG? A: Network Security Group = firewall rules. Control:

Inbound/outbound traffic
Port, protocol, source, destination

Exams & Certification

Q: Is AZ-900 required to take AZ-801? A: No (but recommended). AZ-801 is harder and assumes knowledge.

Q: How long is the AZ-900 exam? A: 45-60 minutes, 40-60 questions.

Q: Can I use study materials during the exam? A: No (proctored), no notes, browsers, or references allowed.

Q: What’s the passing score? A: Approximately 700/1000 (~70%). Score varies by question difficulty.

Q: How long are certifications valid? A: 1 year from passing date. Then must renew.

Common Misconceptions

Q: Is Microsoft 365 part of Azure? A: No (different service). But you can integrate them.

Q: Do I pay Microsoft when my resource is stopped? A: VM: No (if deallocated). Database: Yes (still reserved). Storage: Yes (still storing).

Q: Is private cloud cheaper than public cloud? A: No, usually more expensive (you buy/maintain hardware).

Q: Does Azure backup automatically? A: No (must enable explicitly). Always enable for important data.

Q: Can I access my VM with a keyboard and mouse? A: Yes, via RDP (Remote Desktop) or SSH.

Study Tips ✅

Read thoroughly — Each bullet has exam questions
Understand the Why — Know why you choose a service
Compare services — Understand tradeoffs (cost vs performance)
Take practice exams — Microsoft Learn has free ones
Review failures — Learn from questions you get wrong
Manage time — ~1-1.5 mins per question