Choose an Azure compute service

Azure offers many ways to host your application code. The term compute refers to the hosting model for the resources that your application runs on. This article helps choose a compute service for your application.

Choose a candidate service

Use the following flowchart to select a candidate compute service.

Download a Visio file of this decision tree.

This diagram refers to two migration strategies:

• Lift and shift: A strategy for migrating a workload to the cloud without redesigning the application or making code changes. It's also called rehosting. For more information, see Azure migration and modernization center.
• Cloud optimized: A strategy for migrating to the cloud by refactoring an application to take advantage of cloud-native features and capabilities.

The output from this flowchart is your starting point. Next, evaluate the service to see if it meets your needs.

This article includes several tables that can help you choose a service. The initial candidate from the flowchart might be unsuitable for your application or workload. In that case, expand your analysis to include other compute services.

If your application consists of multiple workloads, evaluate each workload separately. A complete solution can incorporate two or more compute services.

Understand the basic features

If you're not familiar with the Azure service selected in the previous section, see this overview documentation:

• Azure Virtual Machines: A service where you deploy and manage virtual machines (VMs) inside an Azure virtual network.
• Azure App Service: A managed service for hosting web apps, mobile app back ends, RESTful APIs, or automated business processes.
• Azure Functions: A managed function as a service.
• Azure Kubernetes Service (AKS): A managed Kubernetes service for running containerized applications.
• Azure Container Apps: A managed service built on Kubernetes, which simplifies the deployment of containerized applications in a serverless environment.
• Azure Container Instances: This service is a fast and simple way to run a container in Azure. You don't have to provision any VMs or adopt a higher-level service.
• Azure Red Hat OpenShift: A fully managed OpenShift cluster for running containers in production with Kubernetes.
• Azure Spring Apps: A managed service designed and optimized for hosting Spring Boot apps.
• Azure Service Fabric: A distributed systems platform that can run in many environments, including Azure or on-premises.
• Azure Batch: A managed service for running large-scale parallel and high-performance computing (HPC) applications.

Understand the hosting models

For hosting models, cloud services fall into three categories:

• Infrastructure as a service (IaaS): Lets you provision VMs along with the associated networking and storage components. Then you can deploy whatever software and applications you want onto those VMs. This model is the closest to a traditional on-premises environment. Microsoft manages the infrastructure. You still manage the VMs.

• Platform as a service (PaaS): Provides a managed hosting environment where you can deploy your application without needing to manage VMs or networking resources. Azure App Service and Azure Container Apps are PaaS services.

• Functions as a service (FaaS): Lets you deploy your code to the service, which automatically runs it. Azure Functions is a FaaS service.

  Note

  Azure Functions is an Azure serverless compute offering. To see how this service compares with other Azure serverless offerings, such as Logic Apps, which provides serverless workflows, see Choose the right integration and automation services in Azure.

There's a spectrum from IaaS to pure PaaS. For example, Azure VMs can automatically scale by using virtual machine scale sets. This capability isn't strictly a PaaS, but it's the type of management feature found in PaaS.

There's a tradeoff between control and ease of management. IaaS gives the most control, flexibility, and portability, but you have to provision, configure, and manage the VMs and network components you create. FaaS services automatically manage nearly all aspects of running an application. PaaS falls somewhere in between.

Notes

1. If you're using a Consumption plan. For an App Service plan, functions run on the VMs allocated for your App Service plan. See Choose the correct service plan for Azure Functions.
2. Higher service-level agreement (SLA) with two or more instances.
3. Recommended for production environments.
4. Can scale down to zero after job completes.
5. Three for primary nodes and three for worker nodes.
6. When using Durable Functions.

Networking

Notes

1. Requires App Service Environment.
2. Use Azure App Service Hybrid Connections.
3. Requires App Service plan or Azure Functions Premium plan.

DevOps

Notes

1. Options include IIS Express for ASP.NET or node.js (iisnode), PHP web server, Azure Toolkit for IntelliJ, and Azure Toolkit for Eclipse. App Service also supports remote debugging of deployed web app.

Scalability

Notes

1. See Autoscale pods.
2. See Automatically scale a cluster to meet application demands on Azure Kubernetes Service.
3. See Azure subscription and service limits, quotas, and constraints.
4. See Set scaling rules in Azure Container Apps.

Availability

For guided learning on service guarantees, see Core Cloud Services - Azure architecture and service guarantees.

Security

Review and understand the available security controls and visibility for each service:

• Azure Windows virtual machine
• Azure Linux virtual machine
• Azure App Service
• Azure Functions
• Azure Kubernetes Service
• Azure Container Instances
• Azure Spring Apps
• Azure Service Fabric
• Azure Batch

Other criteria

Consider limits and cost

Along with the previous comparison tables, do a more detailed evaluation of the following aspects of the candidate service:

• Service limits
• Cost
• SLA
• Regional availability

Contributors

This article is maintained by Microsoft. It was originally written by the following contributors:

• Ayobami Ayodeji | Senior Program Manager
• Jelle Druyts | Principal Service Engineer
• Martin Gjoshevski | Senior Service Engineer
• Phil Huang | Senior Cloud Solution Architect
• Julie Ng | Senior Service Engineer
• Paolo Salvatori | Principal Service Engineer

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Next steps

Core Cloud Services - Azure compute options. This Learn module explores how compute services can solve common business needs.

Related resources

• Choose an Azure compute option for microservices
• Lift and shift to containers with Azure App Service
• Technology choices for Azure solutions