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Load Balancing in Cloud Computing

Learn about Load Balancing in this comprehensive Cloud Computing tutorial. ALB vs NLB.

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1Layer 7 vs Layer 4

ALB unpacks HTTP packets, allowing intelligent routing. NLB simply forwards TCP streams, making it insanely fast.

2Step-by-Step Breakdown

What is ELB?. Elastic Load Balancing distributes incoming traffic across multiple targets to increase availability.

Application Load Balancer (ALB). Operates at Layer 7 (HTTP/HTTPS). Ideal for modern web apps and microservices.

Path-Based Routing. ALB can route /api to one set of instances and /blog to another.

Network Load Balancer (NLB). Operates at Layer 4 (TCP/UDP). Used for ultra-high performance and low latency.

Knowledge Check. Which load balancer operates at Layer 7 and supports HTTP path routing?

→Network Load Balancer
→Application Load Balancer

Static IPs. NLBs provide a static IP per AZ, whereas ALBs provide a DNS name that resolves to changing IPs.

Target Groups. Load balancers route requests to Target Groups, which contain EC2 instances, IP addresses, or Lambdas.

Health Checks. ELB continually monitors the health of targets. Unhealthy instances are taken out of rotation.

SSL Termination. ALBs can handle SSL/TLS decryption using AWS Certificate Manager (ACM).

Summary. Use ALB for web apps, NLB for raw TCP performance.

Pascual Vila

Frontend Instructor // Code Syllabus

Common Pitfalls & Errors

The Error //

Using an ALB for a workload that needs raw TCP performance or a static IP

aws elbv2 create-load-balancer --name my-nlb --type network --subnets subnet-1 subnet-2

The Solution //

ALB operates at Layer 7 (HTTP/HTTPS) and adds routing overhead that isn't needed for high-throughput TCP/UDP traffic, and it doesn't support static IPs. If the workload needs ultra-low latency, non-HTTP protocols, or a fixed IP, use an NLB (Layer 4) instead.

The Error //

Forgetting to configure health checks that match the app's real readiness

aws elbv2 modify-target-group --target-group-arn <arn> \
  --health-check-path /health --health-check-interval-seconds 15

The Solution //

A health check pointed at the wrong path or port will mark healthy targets as unhealthy (or vice versa), causing the load balancer to route traffic to instances that can't actually serve it. Point the health check at a real readiness endpoint, not just a TCP port check.