Day - 22 | AWS Load Balancers

AWS Load Balancers Explained: ALB vs NLB vs GWLB

As part of my AWS learning journey, I recently explored AWS Elastic Load Balancing (ELB) and its three main load balancer types: Application Load Balancer (ALB), Network Load Balancer (NLB), and Gateway Load Balancer (GWLB).

Each load balancer is designed for a specific purpose and traffic pattern. Choosing the right one is critical for performance, scalability, and security.

In this blog, I’ll explain ALB vs NLB vs GWLB, how they work, and when to use each.

☁️ What is AWS Elastic Load Balancing?

AWS Elastic Load Balancing automatically distributes incoming traffic across multiple targets (EC2 instances, containers, IPs, or Lambda functions). It helps achieve:

• High availability

• Fault tolerance

• Scalability

AWS provides different types of load balancers to handle traffic at different layers of the OSI model.

🌐 Application Load Balancer (ALB)

🔹 What is ALB?

Application Load Balancer (ALB) operates at Layer 7 (Application Layer). It is designed to handle HTTP and HTTPS traffic and makes routing decisions based on content.

🔹 Key Features

• Layer 7 (HTTP/HTTPS)

• Path-based routing (e.g., /api, /login)

• Host-based routing (e.g., api.example.com)

• Supports WebSockets

• Integrates with AWS WAF

• Native support for ECS and Kubernetes

🔹 Use Cases

• Web applications

• Microservices architectures

• REST APIs

• Container-based applications

⚡ Network Load Balancer (NLB)

🔹 What is NLB?

Network Load Balancer (NLB) operates at Layer 4 (Transport Layer) and is built to handle very high throughput and low latency.

🔹 Key Features

• Layer 4 (TCP, UDP, TLS)

• Extremely low latency

• Can handle millions of requests per second

• Preserves client IP address

• Supports static IP addresses

• Suitable for sudden traffic spikes

🔹 Use Cases

• High-performance applications

• Real-time gaming

• Financial systems

• TCP/UDP-based workloads

🔐 Gateway Load Balancer (GWLB)

🔹 What is GWLB?

Gateway Load Balancer (GWLB) is designed to deploy, scale, and manage third-party virtual appliances such as firewalls, intrusion detection systems, and deep packet inspection tools.

It works with transparent network gateways and integrates with VPC traffic flows.

🔹 Key Features

• Operates at Layer 3/4

• Uses GENEVE protocol

• Supports transparent traffic inspection

• Scales security appliances automatically

• Centralized security architecture

🔹 Use Cases

• Network firewalls

• Intrusion detection and prevention systems (IDS/IPS)

• Traffic inspection

• Security compliance enforcement

📊 ALB vs NLB vs GWLB (Comparison)

🧠 How to Choose the Right Load Balancer

• Choose ALB if you need smart routing for HTTP/HTTPS traffic

• Choose NLB if you need extreme performance and low latency

• Choose GWLB if you need centralized security and traffic inspection

There is no one-size-fits-all; the choice depends on your architecture and workload requirements.