Zero-downtime multi-tenant IIS deployments on AWS Elastic Beanstalk

This article demonstrates how to achieve zero-downtime deployments for multi-tenant ASP.NET applications on AWS Elastic Beanstalk by preventing IIS restarts and selectively updating only changed tenants.

• Use skipIISReset flag in deployment manifest to prevent full IIS restarts during deployments
• Implement content-hash change detection in PowerShell scripts to skip unchanged tenant deployments
• Create dedicated IIS application pools per tenant for process isolation and independent recycling
• Deploy infrastructure using CloudFormation with Route 53 private hosted zone for subdomain resolution
• Verify zero-downtime behavior by comparing worker process PIDs before and after deployment

This approach enables updating individual tenant sites independently while keeping unaffected tenants running continuously, eliminating multi-tenant deployment downtime.