Azure containers, ACI and AKS for AZ-900

What a container actually is, and the four Azure services the exam names around it — Container Instances, Kubernetes Service, Container Registry and Container Apps — pinned down with the trigger words that pick each one. AZ-900, 2026 edition.

Here are 7 typical container questions in the exam's own style — free, each answer explained, no sign-up.

Straight to the 7 free questions ↓

Containers show up all over the AZ-900’s compute topics, and candidates lose easy points by blurring four Azure names together. This page slows down on one idea — what a container actually is — and then pins the four services the exam mentions by name. The diagram above lays it out: a container next to a virtual machine, and Azure Container Registry feeding images to the services that run them.

What a container is (and how it differs from a VM)

A container is a lightweight, portable unit that packages an application together with just its dependencies. The key detail the exam wants: a container shares the host operating system’s kernel, so it carries only the app, not a whole OS. That is why a container image is small and starts in seconds, and why you can pack many containers onto one host.

A virtual machine is heavier. It runs its own full guest operating system on top of a hypervisor. That extra OS makes a VM slower to boot and larger, but it gives stronger isolation. So the trade-off is clean: containers win on speed, density and portability; VMs win on isolation. Know that one sentence cold.

The four Azure container services

Sort them into store versus run:

Azure Container Registry (ACR) — the store. A private, managed registry that holds and manages your container images. It never runs a container; the run targets below pull images from it.
Azure Container Instances (ACI) — run one. The simplest way to run a single container fast, with no cluster and no orchestrator, billed per second. Ideal for a quick test or a short-lived job.
Azure Kubernetes Service (AKS) — orchestrate many. Microsoft’s managed Kubernetes: it schedules many containers across a cluster and provides scaling, self-healing and rolling updates. Microsoft manages the control plane; you run the workloads.
Azure Container Apps — serverless containers. Run containers that scale out under load and scale to zero when idle, without operating a Kubernetes cluster yourself.

The trigger words that pick each one

The exam usually hands you a scenario, not a definition. Match the phrasing:

“store and manage container images” → Azure Container Registry
“a single container, fast, no cluster” → Azure Container Instances
“orchestrate,” “self-healing,” “rolling updates,” or “Kubernetes” → Azure Kubernetes Service
“serverless containers, scale to zero, no Kubernetes to manage” → Azure Container Apps

Get those four mappings solid and the container questions turn into free points.

The real exam mixes multiple-choice, true/false, and drag-and-drop formats; the seven questions below are standard multiple-choice, and every explanation carries a “why not the others” so the wrong options teach you as much as the right one.

A two-part diagram of Microsoft Azure containers. The left part contrasts a virtual machine with a container: the VM stack shows hardware, a host operating system, a hypervisor, then a guest full operating system carrying the app, while the container stack shows hardware, a host operating system with its shared kernel, a container runtime, then a lightweight container carrying just the app and its dependencies — the caption notes containers share the host OS kernel, so they are smaller and start in seconds, while a VM ships a whole guest OS and gives stronger isolation. The right part shows Azure Container Registry as a store of container images feeding two run targets: Azure Container Instances running one single container with no cluster, and Azure Kubernetes Service running many containers orchestrated across a cluster with scaling, self-healing and rolling updates. A small note adds Azure Container Apps as serverless containers that scale to zero without managing Kubernetes.

7 free AZ-900 practice questions

Answers and explanations — no email wall

AZ-900 Question 1 of 7

In one interview you are asked why a container is often described as 'lightweight' compared with a virtual machine. What is the defining technical difference the AZ-900 expects?

Answer: A — A container shares the host operating system's kernel and packages only the app and its dependencies, whereas a VM runs its own full guest operating system.

A container virtualizes at the operating-system level: it shares the host's kernel and bundles just the application plus its libraries and dependencies. That is why an image is small and starts in seconds. A VM instead carries a complete guest OS on top of a hypervisor, which is heavier. Why not the others: the language an app is written in has nothing to do with containerization. There is still a host OS — its kernel is shared, not absent — so patching the host still matters. And containers are not Windows-only; Linux containers are the common case. Pro tip: 'shares the host OS kernel, ships only the app + dependencies' is the container definition; 'full guest OS' is the VM.

AZ-900 Question 2 of 7

You have a single containerized image and want it running in Microsoft Azure in seconds — a quick test run, no cluster, no orchestrator, and billing only for the seconds it runs. Which service is the simplest fit?

Answer: A — Azure Container Instances (ACI).

Azure Container Instances runs a container directly, with no cluster or orchestrator to stand up first — the fastest, simplest way to get one container going, billed per second while it runs. Why not the others: AKS gives you a whole managed Kubernetes cluster, which is far more than a single quick container needs. Virtual Machines would make you provision a server and install a container runtime yourself. Container Registry only stores images — it does not run them. Pro tip: 'a single container, fast, no orchestrator' is the ACI signature.

AZ-900 Question 3 of 7

A team is moving a microservices app to Azure. They need many containers scheduled across a pool of nodes, automatic self-healing when a container dies, and rolling updates with no downtime — and they specifically want managed Kubernetes. Which service is designed for this?

Answer: A — Azure Kubernetes Service (AKS).

Azure Kubernetes Service is Microsoft's managed Kubernetes: it schedules many containers across cluster nodes, restarts failed ones (self-healing), scales them, and performs rolling updates — exactly the orchestration described, with Microsoft managing the Kubernetes control plane for you. Why not the others: ACI runs individual containers with no orchestration or self-healing. App Service hosts web apps as a PaaS, not a container cluster you control. Container Registry stores the images the cluster pulls but does not run or orchestrate them. Pro tip: whenever you see 'orchestrate,' 'self-healing,' 'rolling updates,' or the word Kubernetes, the answer is AKS.

AZ-900 Question 4 of 7

Before AKS can pull your custom images, and before ACI can run them, you need a private, secure place inside Azure to store and manage those container images. Which service provides that?

Answer: A — Azure Container Registry (ACR).

Azure Container Registry is a managed, private registry for storing and managing your container images (and related artifacts). AKS and ACI pull the images they run from a registry like ACR. Why not the others: AKS and ACI are run targets — they execute containers, they are not where images live. Blob Storage holds general unstructured files (blobs), not a container registry with image tags and pull semantics. Pro tip: 'store and manage container images' = Azure Container Registry; the run targets (ACI, AKS) pull from it.

AZ-900 Question 5 of 7

A developer wants to deploy containers as a serverless service — code scaling out under load and scaling all the way to zero when idle — without operating a Kubernetes cluster themselves. Which Azure service is built for this?

Answer: A — Azure Container Apps.

Azure Container Apps runs containers serverless: it scales out with demand and can scale to zero when there is no traffic, and you never manage the underlying Kubernetes yourself. Why not the others: AKS also runs containers but hands you the cluster to operate — the opposite of 'no cluster to manage.' Virtual Machines are IaaS servers you fully manage. Container Registry only stores images. Pro tip: 'serverless containers, scale to zero, no Kubernetes to manage' points to Azure Container Apps.

AZ-900 Question 6 of 7

Your team must choose between running a workload in a container and running it on a dedicated virtual machine. Which statement correctly captures the AZ-900 trade-off?

Answer: A — Containers start fast and pack densely because they share the host kernel; a VM boots slower and uses more resources but gives stronger, fuller isolation with its own OS.

Because containers share the host kernel and carry only the app and its dependencies, they are small, start in seconds, and you can pack many on one host. A VM ships a full guest OS, so it is heavier and slower to boot, but that separate OS gives stronger isolation. That density-and-speed versus isolation trade-off is the exam's point. Why not the others: containers are prized for portability, not penalized for it. A VM is heavier, not lighter, and it does have an OS. And the two are clearly different models, not synonyms. Pro tip: containers = light, fast, dense (shared kernel); VMs = heavier, stronger isolation (own OS).

AZ-900 Question 7 of 7

A colleague lists four Azure names — Container Registry, Container Instances, Kubernetes Service, and Container Apps — and asks which one only stores images and never runs a container. Which is it?

Answer: A — Azure Container Registry.

Azure Container Registry is the storage service — it holds and manages container images that the other services pull and run. The other three are run targets: Container Instances runs a single container, Kubernetes Service orchestrates many across a cluster, and Container Apps runs containers serverless. Why not the others: each of those three executes containers, so none of them is the 'store only, never run' answer. Pro tip: sort the four into store versus run — ACR stores; ACI, AKS and Container Apps run.

That is exactly how every question in the course works — answer, explanation, why-not. The real set continues in the practice player: 10 free questions, no sign-up.

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Frequently asked questions

What is the difference between a container and a virtual machine?

A container shares the host operating system's kernel and packages only the application and its dependencies, so it is small and starts in seconds, and you can run many on one host. A virtual machine runs its own full guest operating system on top of a hypervisor, which is heavier and slower to start but gives stronger isolation. In short: containers trade some isolation for speed, density and portability; VMs trade weight for a fully separate OS.

When do I use Azure Container Instances instead of Azure Kubernetes Service?

Use Azure Container Instances (ACI) to run a single or short-lived container fast, with no cluster or orchestrator to set up. Use Azure Kubernetes Service (AKS) when you need to orchestrate many containers across a cluster — with scaling, self-healing and rolling updates. One container, no cluster: ACI. Many containers, managed at scale: AKS.

Are these real exam questions?

No. They are our own questions, written in the style and difficulty of the AZ-900 — never copied from any question bank or the real exam. Reproducing live exam items violates Microsoft's certification agreement and can cost a candidate their certification, and a crammed answer teaches you nothing about the one you have not seen.

Updated for AZ-900 (July 2026). The sample questions above are our own work in the style of the exam — not real exam items. The exam itself is set and marked by the certification body.