Why PaaS Compute?
Running apps on VMs gives control, but it also means managing OS patches, scaling, and availability. Azure App Service provides a Platform-as-a-Service (PaaS) environment where you focus on your app code, and Microsoft handles the infrastructure.
As a Solution Architect, your role is to decide when App Services are a better fit than IaaS VMs or containers.
Azure App Service
Definition:
A fully managed hosting platform for web apps, REST APIs, and mobile app backends.
Key Features:
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Supports multiple runtimes (.NET, Java, Python, Node.js, PHP).
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Built-in CI/CD integration with GitHub, Azure DevOps.
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Autoscaling and load balancing built-in.
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Custom domains and SSL certificates.
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Integration with VNETs for secure backends.
Best Use Cases:
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Customer-facing web apps.
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APIs needing rapid deployment and scaling.
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SaaS applications without infrastructure overhead.
App Service Plans
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Determines region, scaling, and pricing.
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Tiers:
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Free/Shared → basic testing.
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Basic/Standard → production workloads.
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Premium → high-scale apps with VNET integration.
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Isolated → dedicated environment, used with App Service Environment (ASE).
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App Service Environment (ASE)
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Dedicated, fully isolated environment for App Services.
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Provides enhanced VNET integration and security.
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Used by enterprises with strict compliance.
Design Considerations
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Scaling
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Horizontal scaling (scale out with more instances).
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Vertical scaling (scale up with higher SKU).
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Networking
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Use Private Endpoints or ASE for sensitive apps.
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Integrate with VNets if backend resources must remain private.
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High Availability
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Deploy across multiple Availability Zones where supported.
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Use Traffic Manager or Front Door for global failover.
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Security
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Integrate with Managed Identities for secure access to Key Vault and other services.
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Apply WAF via Application Gateway or Front Door.
Example Enterprise Scenario
A retail company wants to:
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Deploy a web app for global customers.
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Ensure autoscaling during peak seasons.
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Securely connect the app to a backend database in a private VNET.
Correct design:
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Use App Service Premium Plan with VNET integration.
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Enable autoscaling rules.
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Secure backend access with Private Endpoint for SQL.
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Use Front Door for global distribution.
Confusion Buster
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App Service vs VM
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VM = full control, manual patching.
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App Service = managed PaaS, no OS management.
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App Service vs AKS
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App Service = best for simple apps/APIs.
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AKS = best for containerized, microservices architectures.
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App Service vs Functions
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App Service = long-running web apps.
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Functions = event-driven, short-lived tasks.
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Exam Tips
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“Which service hosts web apps with minimal infra management?” → App Service.
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“Which option provides fully isolated environment for compliance?” → ASE.
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“Which scaling method adds more instances?” → Horizontal scaling.
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“Which tier integrates with VNets?” → Premium/Isolated.
What to Expect in the Exam
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Direct Q: “Which Azure service provides PaaS hosting for web applications?” → App Service.
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Scenario Q: “Company requires secure web app with VNET backend integration.” → App Service Premium/ASE.
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Scenario Q: “Global app with automatic scaling for user traffic.” → App Service + Front Door.
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Trick Q: “App Services require you to patch OS manually.” → False.