AZ-900 Describe Azure architecture and services Practice Question
Which Azure service enables serverless compute for running containers with scale-to-zero capabilities?
⚠ Common exam trap
Candidates often confuse Azure Container Apps with Azure Container Instances (ACI) because both are described as 'serverless containers,' but ACI lacks automatic scale-to-zero and has a minimum billing duration, whereas Container Apps is designed specifically for that capability.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Azure Container Apps
Azure Container Apps is the correct answer because it is a fully managed serverless container service that automatically scales down to zero when there is no traffic, meaning you only pay for resources when your containers are actively running. This scale-to-zero capability is a key differentiator from other container services, as it allows cost-efficient execution of event-driven or idle workloads without maintaining a running cluster.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Azure Functions
Why it's wrong here
Azure Functions is a serverless compute service optimized for running individual pieces of code triggered by events, with built-in bindings and triggers for HTTP, queues, timers, and more. Although Functions supports custom Linux containers, its scaling model is fundamentally based on function executions in the Consumption or Premium plans, not on managing multiple container replicas with KEDA-driven autoscaling across arbitrary images. Since the question asks about full containerized applications with scale-to-zero, Functions is a code-centric service rather than a general-purpose container hosting platform, so Container Apps is the better answer.
- ✓
Azure Container Apps
Why this is correct
Azure Container Apps is a serverless container platform designed specifically for running full containerized applications and microservices without managing Kubernetes infrastructure. It natively integrates with KEDA (Kubernetes Event-driven Autoscaling) and supports true scale-to-zero, meaning a revision can have zero replicas when no events are incoming and automatically scale out in response to HTTP requests, queue messages, or custom triggers. It also provides built-in service discovery, Dapr integration, and revision-based versioning, making it the correct choice for event-driven containerized workloads that need to pause entirely when idle.
- ✗
Azure Kubernetes Service
Why it's wrong here
Azure Kubernetes Service (AKS) is a managed Kubernetes orchestration platform that still requires a provisioned cluster of virtual machines, including at least one worker node per node pool. Even with the cluster autoscaler, the minimum node count is typically 1, so you cannot scale to zero replicas or zero nodes. You are always paying for and managing the underlying VM infrastructure, whereas Container Apps abstracts the entire orchestrator and can scale a revision to zero replicas when idle.
- ✗
Azure Container Instances
Why it's wrong here
Azure Container Instances (ACI) runs individual containers on demand without requiring you to provision virtual machines, but it does not provide native event-driven autoscaling or a scale-to-zero orchestration model. Each container group is a discrete, statically deployed instance; you must manually start or stop instances or use an external scheduler, as ACI itself does not monitor KEDA triggers such as queue depth or HTTP traffic to change its replica count. ACI is ideal for short, event-driven bursts, but it lacks the integrated autoscaling from zero that Container Apps offers.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
Go deeper
Related to this question
Learn chapter
Azure Regions and Geographies
Key term
Serverless
Serverless is a cloud computing model where the cloud provider manages the servers, and you only pay for the actual compute time your code uses, without having to worry about provisioning or maintaining infrastructure.
Key term
Container
A container is a lightweight, standalone software package that includes everything needed to run an application, such as code, runtime, system tools, and libraries.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-900 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-900 exam.