What is AWS Load Balancer?
AWS Load Balancer (ELB) is a cloud service that distributes incoming traffic across multiple servers to improve performance, availability, and security. It helps prevent server overload, ensures fault tolerance, and enables auto-scaling.
Why Do You Need AWS Load Balancer?
- Scalability: Handles high traffic efficiently.
- Fault Tolerance: Routes traffic to healthy instances.
- Security: Supports SSL/TLS termination & AWS WAF.
- Cost Optimization: Works with auto-scaling to reduce unnecessary server usage.
Types of AWS Load Balancers
1. Application Load Balancer (ALB)
- Works at Layer 7 (Application Layer).
- Supports HTTP/HTTPS traffic.
- Enables path-based & host-based routing.
- Ideal for microservices, APIs, and modern web applications.
Best for: Web applications, API gateways, containerized workloads.
2. Network Load Balancer (NLB)
- Works at Layer 4 (Transport Layer).
- Supports TCP, UDP, and TLS traffic.
- Offers low latency and high throughput.
- Maintains static IP addresses.
Best for: Real-time applications, gaming, and financial services.
3. Gateway Load Balancer (GWLB)
- Works at Layer 3 (Network Layer).
- Routes traffic to third-party security appliances.
- Useful for firewalls, intrusion detection, and DDoS protection.
Best for: Security services, centralized traffic inspection.
4. Classic Load Balancer (CLB) [Legacy]
- Supports both Layer 4 & Layer 7 but lacks advanced features.
- AWS recommends using ALB or NLB instead.
Best for: Legacy applications that haven’t migrated to newer ELB types.
Key Features of AWS Load Balancer
- Auto Scaling: Automatically adjusts instances based on traffic.
- Cross-Zone Load Balancing: Distributes traffic across multiple AZs.
- SSL/TLS Termination: Improves security for HTTPS connections.
- Access Logs & Monitoring: Integrated with CloudWatch, AWS WAF.
- High Performance: Handles millions of requests per second.
AWS Load Balancer Architecture & Traffic Flow
How AWS Load Balancer Works?
- A user request enters AWS through Route 53 (DNS).
- The ALB/NLB/GWLB routes traffic based on rules.
- It forwards requests to healthy EC2 instances or containers.
- AWS Auto Scaling adds or removes instances based on demand.
- If an instance fails, ELB reroutes traffic to healthy ones.
Best Practices for AWS Load Balancer Security
1. Use HTTPS & SSL/TLS
- Protect sensitive data by enabling SSL certificates from AWS Certificate Manager (ACM).
- Prefer TLS 1.2 or TLS 1.3 for stronger encryption.
2. Enable AWS WAF (Web Application Firewall)
- Protect against SQL injection, XSS, and DDoS attacks.
- Use custom rules to filter malicious traffic.
3. Restrict Access with Security Groups
- Allow traffic only from trusted sources.
- Set up IAM roles for controlled access.
Performance Optimization Tips for AWS Load Balancer
1. Enable HTTP/2 for Faster Load Times
- Reduces latency with multiplexing & compression.
2. Optimize Health Checks
- Set appropriate thresholds to detect failing instances.
3. Use Cross-Zone Load Balancing
- Distributes traffic evenly across multiple Availability Zones (AZs).
4. Integrate with CloudFront CDN
- Cache static content to reduce server load and boost speed.
5. Reduce Connection Overhead
- Enable keep-alive for persistent connections.
Pricing & Cost Optimization
How is AWS Load Balancer Pricing Calculated?
- Hourly Load Balancer charges.
- Data processing fees (per GB).
- Additional costs for AWS WAF, CloudFront, and logging.
Tips to Reduce Costs:
- Use Auto Scaling to optimize resources.
- Remove unused Load Balancers to avoid unnecessary billing.
- Leverage Spot Instances for backend servers.
Choosing the Right Load Balancer for Your Application
| Feature | ALB | NLB | GWLB |
| Layer | Layer 7 (Application) | Layer 4 (Network) | Layer 3 (Gateway) |
| Protocols | HTTP, HTTPS | TCP, UDP, TLS | Any IP traffic |
| Best for | Web apps, APIs, Microservices | High-speed, low-latency workloads | Security appliances, firewalls |
| Performance | Good for standard apps | Handles millions of requests/sec | Routes to security appliances |
Final Thoughts
AWS Load Balancer is essential for scalable, highly available, and secure applications. By choosing the right Load Balancer, implementing security best practices, and optimizing configurations, businesses can enhance performance, improve reliability, and reduce costs.