App Service

Azure App Service is a managed PaaS for web apps, APIs, and background workers. You deploy code or containers, map custom domains, terminate TLS, and scale by instance count or autoscale rules without managing VMs.

| Feature | Interview relevance | |---------|-------------------| | Deployment slots | Staging swap with warm-up and rollback | | App settings | Environment-specific config and connection strings | | Always On | Keeps idle apps warm; affects cold-start behavior | | VNet integration | Private access to databases and internal APIs |

					az webapp deployment slot create --name api --resource-group rg --slot staging
az webapp deployment slot swap --name api --resource-group rg --slot staging
				

On interviews: when App Service beats AKS or Functions; slot swap versus blue/green; scaling limits; managed identity to Azure SQL or Blob Storage; and how you would roll back a bad deploy.

Common pitfalls: storing secrets in app settings without Key Vault references; slot settings that drift from production; Always Off on production APIs; and treating local filesystem as durable storage.

The trade-off is operational simplicity and fast deploys versus less control over the runtime, networking, and scaling granularity than containers on AKS.

Checklist:

• Use deployment slots for zero-downtime releases.
• Externalize secrets via Key Vault references.
• Enable autoscale with sane min/max bounds.
• Integrate VNet when data plane must stay private.
• Monitor HTTP 5xx, latency, and CPU/memory saturation.