The Ultimate AWS Load Balancer Comparison: ALB, NLB, and GLB Explained

As applications scale and demand high availability and performance, load balancers are crucial in efficiently distributing traffic. Amazon Web Services (AWS) offers several load balancers tailored to specific use cases. In this comprehensive guide, we’ll compare Application Load Balancer (ALB), Network Load Balancer (NLB), and Gateway Load Balancer (GLB) to help you choose the right one for your architecture.

---

What Is a Load Balancer?

A load balancer distributes incoming network traffic across multiple targets—such as EC2 instances, containers, and IP addresses—to ensure no single server demands too much. AWS’s Elastic Load Balancing (ELB) service offers three types of load balancers to suit different needs.

---

AWS Application Load Balancer (ALB)

Key Features:

• Layer 7 (Application Layer) load balancing
  
  

• Supports host-based and path-based routing
  
  

• Works with HTTPS, WebSockets, and HTTP/2
  
  

• Ideal for microservices and containerized applications
  
  

• Native integration with Amazon ECS, EKS, and Lambda
  
  

Use Cases:

• Routing user traffic to different services based on URL paths
  
  

• Hosting multiple websites on the same load balancer
  
  

• TLS termination and SSL offloading
  
  

---

AWS Network Load Balancer (NLB)

Key Features:

• Operates at Layer 4 (Transport Layer)
  
  

• Handles millions of requests per second
  
  

• Supports TCP, TLS, and UDP protocols
  
  

• Extremely low latency
  
  

• Preserves source IP for end-to-end visibility
  
  

Use Cases:

• High-performance applications requiring static IP addresses
  
  

• Real-time gaming, streaming, or financial applications
  
  

• Load balancing for internal services with PrivateLink support
  
  

---

AWS Gateway Load Balancer (GLB)

Key Features:

• Operates at Layer 3 (Network Layer)
  
  

• Integrates with third-party virtual appliances like firewalls and intrusion detection systems (IDS)
  
  

• Provides transparent traffic inspection
  
  

• Uses GWLBE (Gateway Load Balancer Endpoints) to route traffic securely across VPCs
  
  

Use Cases:

• Deploying network security appliances at scale
  
  

• Centralized traffic inspection in multi-VPC architectures
  
  

• Enabling partner security solutions in a service VPC
  
  

---

Comparison Table: ALB vs. NLB vs. GLB

Feature: Layer

• ALB: Operates at Layer 7 (Application)
  
  

• NLB: Operates at Layer 4 (Transport)
  
  

• GLB: Operates at Layer 3 (Network)
  
  

Feature: Protocols Supported

• ALB: HTTP, HTTPS, WebSocket
  
  

• NLB: TCP, UDP, TLS
  
  

• GLB: IP
  
  

Feature: Use Case Focus

• ALB: Web applications, microservices
  
  

• NLB: High-throughput services
  
  

• GLB: Security appliances
  
  

Feature: IP Address Retention

• ALB: No
  
  

• NLB: Yes
  
  

• GLB: Yes
  
  

Feature: SSL Termination

• ALB: Yes
  
  

• NLB: Yes
  
  

• GLB: No
  
  

Feature: Health Checks

• ALB: HTTP/HTTPS
  
  

• NLB: TCP/HTTP/HTTPS
  
  

• GLB: TCP
  
  

Feature: Path/Host-based Routing

• ALB: Yes
  
  

• NLB: No
  
  

• GLB: No
  
  

Feature: Pricing

• ALB: Based on LCU (Load Balancer Capacity Units) plus data processed
  
  

• NLB: Charged per GB plus per hour
  
  

• GLB: Based on usage and appliances used

---

Choosing the Right AWS Load Balancer

Here’s a simple rule of thumb:

• Use ALB for web applications needing intelligent routing.
  
  

• Choose NLB for performance-intensive, latency-sensitive workloads.
  
  

• Opt for GLB when integrating third-party security services or traffic inspection across multiple VPCs.
  
  

---

Conclusion

Each AWS load balancer type serves a unique purpose. The Application Load Balancer excels in content-based routing, the Network Load Balancer handles raw performance needs, and the Gateway Load Balancer empowers network security. Understanding your application’s architecture and traffic patterns is key to selecting the best option.