Azure compute is one of the most heavily tested domains on the AZ-900 exam. Microsoft tests your ability to choose the right compute service for a given scenario — not deep technical configuration. This guide covers each major compute service, when to use it, and the IaaS vs PaaS distinction that underpins every exam question. Use it alongside our AZ-900 practice tests to reinforce each concept before exam day.

Azure Virtual Machines

Azure Virtual Machines (VMs) are the foundational IaaS compute offering. When you create a VM, you get a virtualized server in the cloud where you control the operating system, installed software, security patches, and runtime environment. This maximum control comes with maximum responsibility — the AZ-900 exam frequently tests this trade-off. VMs are the right choice when you need to lift-and-shift an existing on-premises server to the cloud without refactoring the application, or when your workload requires a specific OS configuration that a managed service cannot provide. Key VM concepts for AZ-900: - Availability Sets — protect VMs from rack-level failures by distributing across fault and update domains - Availability Zones — protect against datacenter failure by placing VMs in separate physical zones within a region - VM Scale Sets — automatically increase or decrease the number of VM instances based on demand - Azure Spot VMs — use unused Azure capacity at steep discounts, but can be evicted when capacity is needed

App Service, Containers, and Kubernetes

When developers want to deploy web applications without managing servers, Azure App Service is the go-to PaaS solution. App Service handles OS patching, load balancing, auto-scaling, and SSL certificates automatically. You simply deploy your code (Node.js, Python, .NET, Java, PHP, or containers) and Azure runs it. App Service is the AZ-900 answer whenever a scenario describes a company that wants to run a web app or REST API without worrying about the underlying infrastructure. It supports continuous deployment from GitHub, Azure DevOps, and other repositories. For containerized workloads, Azure offers two core services: Azure Container Instances (ACI) is the simplest way to run a container in Azure. There's no cluster to manage — you define the container image, CPU, and memory, and ACI starts it within seconds. ACI is PaaS and suits short-lived, single-container tasks, batch jobs, and testing scenarios. Azure Kubernetes Service (AKS) is a fully managed Kubernetes orchestration platform. It suits complex, multi-container applications that need auto-scaling, rolling updates, service discovery, and high availability. AKS is the answer when an exam question mentions Kubernetes, microservices at scale, or orchestration. Also covered in AZ-900 is Azure Virtual Desktop — a desktop and application virtualization service that lets users run a full Windows desktop environment from any device. It's often tested in scenarios involving remote work, bring-your-own-device (BYOD) policies, or centralizing application delivery. Read more about Azure deployment options in our AZ-900 complete guide.

Serverless Computing and Azure Functions

Serverless computing means you write and deploy code without thinking about servers at all — Azure allocates compute dynamically when your code runs and releases it immediately after. Azure Functions is the primary serverless offering on Azure. Functions are triggered by events: an HTTP request, a message arriving in a storage queue, a timer schedule, a new file in blob storage, and many others. Each function execution is independent and stateless. Billing is based on the number of executions and their duration, so you pay nothing when your code is not running. For AZ-900, the key serverless scenarios are: - Running small pieces of code in response to events (HTTP trigger, timer, queue message) - Building event-driven architectures without provisioning infrastructure - Tasks where workload is unpredictable and you want automatic scaling to zero Azure Functions can also be compared to Azure Logic Apps, which is a low-code/no-code workflow automation tool. Where Functions are code-first, Logic Apps are designer-first with hundreds of connectors to external services. Both are serverless, but exam questions distinguish them by whether a developer writes code or drags and drops connectors. Understanding serverless is also key to the AZ-900 governance and compliance domain, since serverless services eliminate infrastructure you need to patch and audit.

Compute services connect directly to Azure's networking and storage layers. Virtual Machines attach to virtual networks and network security groups (covered in our AZ-900 networking guide). App Service and Functions store data in Azure Storage or databases (see AZ-900 storage services). Understanding how compute integrates with these layers is essential for scenario questions on the exam.

AZ-900 Compute Exam Tips

Ready to test your knowledge? Our free AZ-900 practice tests include dedicated compute scenario questions covering VM selection, PaaS vs IaaS trade-offs, serverless patterns, and container orchestration. Pair this guide with the AZ-900 complete guide for full exam coverage.