AWS ALB vs NLB vs CLB – Load Balancers Explained with Use Cases ⚖️☁️

"Three load balancers walk into a cloud... Which one do you choose?"

When building apps on AWS, choosing the right load balancer isn’t just a tech decision — it's the difference between blazing-fast traffic routing and a clogged request pipeline.

In this post, we’ll break down AWS's 3 load balancer types — ALB, NLB, and CLB — in beginner-friendly terms, backed by real-world analogies and practical use cases.

Ready to route your traffic like a pro? Let’s go. 🚦

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🚀 What Is a Load Balancer?

A load balancer is like a smart traffic cop that:

• Distributes incoming traffic to healthy backend servers (EC2s, containers, etc.)

• Helps scale apps

• Increases fault tolerance

• Ensures high availability

Think of it like a receptionist at a clinic directing patients (users) to available doctors (EC2s).

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🧠 Meet the Trio: ALB, NLB, CLB

1. ALB (Application Load Balancer)

• Works at Layer 7 (Application Layer)

• Smart routing: based on URL, headers, methods, etc.

• Best for HTTP/HTTPS apps, REST APIs, microservices

• Supports WebSockets, path-based routing, and host-based routing

2. NLB (Network Load Balancer)

• Works at Layer 4 (Transport Layer)

• Handles millions of requests/sec with ultra-low latency

• Ideal for TCP, TLS, and UDP traffic

• Supports static IP and Elastic IP

3. CLB (Classic Load Balancer)

• The OG balancer (pre-2016)

• Mix of Layer 4 and Layer 7

• Legacy workloads

• Not recommended for new architectures

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🧭 Real-Life Analogy: Choosing the Right Receptionist

• ALB = Receptionist who listens to patient symptoms and directs based on specialization (e.g., "Go to ENT")

• NLB = Receptionist who routes based only on department number (e.g., "Cardiology = Room 5")

• CLB = Old receptionist who does both jobs but isn’t as efficient

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📊 Feature Comparison Table

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🧰 Use Cases: When to Use What?

✅ Use ALB When:

• You're running microservices or containerized apps (like ECS or EKS)

• You need host/path-based routing (e.g., /api, /blog)

• You want to serve HTTPS traffic + SSL termination

• You need to route to Lambda functions

✅ Use NLB When:

• You need extremely low latency and high throughput

• You’re handling TCP or UDP traffic (e.g., game servers, VPNs)

• You require static IP addresses

• You want to support TLS passthrough

🚫 Avoid CLB Unless:

• You're dealing with legacy apps that were built around CLB

• You need a quick and dirty setup for basic web hosting (still not recommended long-term)

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🧪 Quick Setup Tip (ALB + ECS)

# Sample ECS service creation with ALB
aws ecs create-service \
  --cluster my-cluster \
  --service-name my-service \
  --load-balancers targetGroupArn=xxx,containerName=my-app,containerPort=80 \
  --launch-type FARGATE \
  --task-definition my-task \
  --desired-count 2

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📦 Summary: Make the Smart Call

In short: ALB = Smart HTTP, NLB = Speed Demon, CLB = Grandpa

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💬 What’s Your Load Balancer Story?

Ever made the wrong choice and paid the price?
Or found a clever use for NLB in a real-time app?

👇 Drop your tips, questions, and war stories in the comments.
Smash that ❤️ if you learned something, and share with a dev buddy juggling load balancer chaos.

Let’s route traffic like pros. 🧡