Integrating CloudFront with Application Load Balancer (ALB) for Sticky Sessions

• Objective: To maintain session affinity between users and backend EC2 instances using CloudFront and ALB with sticky sessions enabled.
• Sticky Sessions: Ensures that requests from the same user are routed to the same backend EC2 instance.
• CloudFront and ALB Integration:
  • Problem Statement: Without proper configuration, CloudFront may not forward the session affinity cookie to the ALB, disrupting the sticky session mechanism.
  • Solution: Forward the session affinity cookie (e.g., AWSALB cookie) from CloudFront to the ALB to maintain session affinity.
• Implementation Steps:
  1. Cookie Forwarding: Whitelist the session affinity cookie (AWSALB) in CloudFront's configuration to ensure it is forwarded to the ALB.
  2. Session Persistence: The ALB recognizes the forwarded cookie and routes requests to the appropriate EC2 instance based on the cookie value.
  3. Different Users Handling: Each user's requests carry a unique AWSALB cookie value, enabling the ALB to maintain separate sticky sessions.

• Security Measures:
  • Time-to-Live (TTL) Configuration: Set a TTL for cached requests in CloudFront to a value less than the lifespan of the authentication cookie to enhance security.
• Note: While crucial for maintaining session affinity in this setup, these detailed configurations are beyond the scope of certification exams but are important for practical applications.
• Conclusion: Properly integrating CloudFront with ALB using sticky sessions requires careful forwarding of session cookies and TTL settings to ensure secure and consistent user sessions.