Compute choices: VMs, containers, and functions¶

Azure offers several ways to run code and workloads. The exam tests which compute option fits a scenario, not deep implementation details.

Compare the main options¶

Option	You manage	Azure manages	Best when
Virtual Machines (IaaS)	OS, apps, patching, scaling design	Physical hosts and hypervisor	Lift-and-shift, full OS control, legacy apps
Azure Container Instances	Container image and app	Underlying host for the container	Simple, quick container runs without orchestrating a cluster
Azure Kubernetes Service (AKS)	Containers, manifests, app design	Managed Kubernetes control plane	Container orchestration at scale
Azure Functions (serverless)	Function code and triggers	Runtime scaling and underlying infrastructure	Event-driven, short-lived tasks without server admin

Virtual Machines¶

Choose a VM when the scenario mentions:

control of the operating system;
installing custom or legacy software;
migrating an on-premises server with minimal change;
running software that is not containerized or supported on PaaS.

VMs offer the most control and the most operational responsibility among common compute choices.

Containers¶

Containers package an application with its dependencies so it runs consistently across environments.

Azure Container Instances (ACI): run one or more containers without managing cluster infrastructure.
Azure Kubernetes Service (AKS): run and orchestrate many containers with scaling, networking, and deployment automation.

Exam clue: need containers without managing servers → Container Instances or a managed Kubernetes service such as AKS, depending on scale and orchestration needs.

Azure Functions¶

Functions run code in response to triggers such as HTTP requests, timers, queue messages, or blob uploads.

Typical serverless clues:

run code only when an event happens;
no server administration;
automatic scaling on eligible plans;
short-lived processing.

Serverless does not mean no servers exist. It means the customer does not provision or manage them.

Decision flow¶

Need full OS control or legacy server?
  └── Yes → Virtual Machine
  └── No → Need a long-running web/API platform?
        └── Yes → see Application hosting lesson
        └── No → Event-driven short task?
              └── Yes → Azure Functions
              └── No → Container workload?
                    └── Simple run → Container Instances
                    └── Orchestrated fleet → AKS

Scenario¶

An image-processing job should run for a few seconds whenever a file is uploaded to storage. The team does not want to patch servers.

Best fit: Azure Functions. The upload is the trigger; execution scales with demand.

Exam clues¶

Patch the operating system → VM, not Functions or Container Instances alone.
Upload triggers small code → Azure Functions.
Run a container quickly without a cluster → Azure Container Instances.
Manage many microservices at scale → AKS.