If you're building on AWS, choosing the right load balancer is critical.
ALB is for HTTP apps, NLB is for high performance, and CLB is legacy — but the real differences matter.
This guide breaks down exactly when to use each.
🧠 What is a Load Balancer in AWS?
A load balancer distributes incoming traffic across multiple servers to ensure:
- High availability
- Scalability
- Fault tolerance
AWS provides three types:
- Application Load Balancer (ALB)
- Network Load Balancer (NLB)
- Classic Load Balancer (CLB)
⚡ AWS ALB vs NLB vs CLB (Quick Comparison)
| Feature | ALB | NLB | CLB |
|---|---|---|---|
| Layer | Layer 7 (HTTP/HTTPS) | Layer 4 (TCP/UDP) | Layer 4/7 |
| Performance | Medium | Ultra High | Low |
| Routing | Path-based | IP-based | Basic |
| Use Case | Web apps, APIs | Gaming, real-time | Legacy apps |
🔷 Application Load Balancer (ALB)
Best for modern web applications.
- Works at Layer 7
- Supports HTTP/HTTPS
- Path-based routing (/api, /app)
- Host-based routing
Example:
Route /api → backend API
Route /app → frontend service
👉 Use ALB for:
- Microservices
- REST APIs
- Web applications
🔶 Network Load Balancer (NLB)
Best for extreme performance and low latency.
- Works at Layer 4
- Handles millions of requests/sec
- Static IP support
- Ultra low latency
Example:
Real-time gaming server or financial system
👉 Use NLB for:
- High-performance systems
- TCP/UDP workloads
- IoT, gaming
⚠️ Classic Load Balancer (CLB)
Legacy load balancer — avoid for new projects.
- Limited features
- No advanced routing
- Being phased out
👉 Only use if maintaining old systems.
⚡ When to Use Each
- Use ALB → Web apps, APIs, microservices
- Use NLB → High performance, TCP/UDP
- Use CLB → Legacy only
❌ Common Mistakes
- Using NLB for HTTP apps ❌
- Using CLB in new architecture ❌
- Ignoring latency requirements ❌
💡 Pro Architecture Tip
Many production systems use both:
- ALB → handles HTTP routing
- NLB → handles performance-critical traffic
👉 Hybrid architecture = best scalability.
🔗 Learn by Doing (Hands-On Labs)
🔗 Related Articles
❓ FAQs
Which load balancer is best in AWS?
ALB is best for web apps, while NLB is best for high-performance workloads.
Is CLB deprecated?
CLB is not fully deprecated but is no longer recommended for new applications.
Can I use ALB and NLB together?
Yes, many production systems combine both for flexibility and performance.
Does ALB support TCP?
No, ALB only supports HTTP/HTTPS. Use NLB for TCP/UDP.