3.4 Reliability Improvement

Failure Management

Removing Single Points of Failure (SPOF)

• Pattern 1: One EC2 → ASG with min 2 across AZs.
• Pattern 2: One RDS → RDS Multi-AZ Standby.
• Pattern 3: Direct Connect → Direct Connect with VPN Backup or active/active DX.

Load Balancing

• Application Load Balancer (ALB): Layer 7 (HTTP/HTTPS). Path/Host routing. WAF integration. Container support (Dynamic ports).
• Network Load Balancer (NLB): Layer 4 (TCP/UDP). Ultra-high performance. Static IPs.
• Gateway Load Balancer (GWLB): Layer 3. Used for firewalls/appliances (GENEVE protocol).

WARNING

Exam Gotcha: If you need a Static IP for your Load Balancer, you must use NLB. ALB does not support static IPs (its DNS name resolves to changing IPs). If you need WAF, you must use ALB or CloudFront.

Auto Scaling

• Predictive Scaling: Machine Learning scans history to forecast load and schedule scaling actions before the spike.
• Warm Pools: Pre-initialized instances (stopped state) to reduce boot time.