AWS Load Balancers

AWS provides Elastic Load Balancing (ELB) services to automatically distribute incoming application traffic across multiple targets, such as Amazon EC2 instances, containers, IP addresses, and Lambda functions.

Load balancers help improve fault tolerance, scalability, and availability.

Types of AWS Load Balancers

1. Application Load Balancer (ALB)

Operates at Layer 7 (HTTP/HTTPS).
Best for web applications.
Supports advanced routing:
- Path-based (e.g., /images → one service, /api → another service).
- Host-based (e.g., api.example.com vs app.example.com).
Integrates with AWS WAF and CloudWatch.

2. Network Load Balancer (NLB)

Operates at Layer 4 (TCP, UDP, TLS).
Handles millions of requests per second with ultra-low latency.
Best for:
- Real-time gaming.
- IoT applications.
- High-performance workloads.

3. Gateway Load Balancer (GWLB)

Operates at Layer 3 (Network Layer).
Deploys, scales, and manages third-party virtual appliances (e.g., firewalls, intrusion detection, deep packet inspection).
Routes traffic using Geneve protocol.

4. Classic Load Balancer (CLB) (Legacy)

Works at both Layer 4 and Layer 7.
Limited features, mainly for older applications.
Recommended to migrate to ALB or NLB.

Key Features

High Availability – Automatically distributes traffic across multiple AZs.
Health Checks – Routes traffic only to healthy targets.
SSL/TLS Termination – Offloads encryption from application servers.
Integration – Works with Auto Scaling, CloudWatch, Route 53, and WAF.
Security – Supports Security Groups and IAM policies.

Use Cases

ALB → Microservices, APIs, web apps.
NLB → Gaming, streaming, IoT, financial apps.
GWLB → Security appliances (firewalls, packet inspection).
CLB → Legacy workloads (not recommended for new apps).

Example: Architecture Diagram

   Clients
      |
   [AWS Route 53]
      |
   [Elastic Load Balancer]
    /           \
 [EC2-1]      [EC2-2]