📖 What is Elastic Load Balancing (ELB)?
Elastic Load Balancing (ELB) automatically distributes incoming application traffic across multiple targets, improving application availability and scalability. ELB monitors the health of targets and routes traffic only to healthy instances, ensuring fault tolerance and optimal performance.
"Master the distinctions between ALB, NLB, and Classic Load Balancer. ALB is for HTTP/HTTPS traffic, NLB for TCP/UDP, and Classic Load Balancer is the older generation. Understand the features of each, including support for sticky sessions, health checks, and target groups. Exam questions frequently present scenarios requiring the selection of the appropriate ELB type."
📚 Certification: AWS Certified Solutions Architect - Associate (SAA-C03)
🔑 What are the Key Concepts of Elastic Load Balancing (ELB)?
- ▸ ALB (Application Load Balancer) operates at the application layer (Layer 7) and supports HTTP/HTTPS traffic with features like content-based routing.
- ▸ NLB (Network Load Balancer) functions at the transport layer (Layer 4) and is ideal for TCP/UDP traffic, handling millions of requests per second.
- ▸ Classic Load Balancer is the older generation, supporting both Layer 4 and Layer 7, but lacks features of newer ELB types and is generally not recommended.
- ▸ Target groups define the targets (EC2 instances, containers, IP addresses) that receive traffic from the load balancer, enabling flexible scaling and management.
- ▸ Health checks are crucial for ELB functionality, ensuring traffic is routed only to healthy instances and maintaining high availability.
🎯 How does Elastic Load Balancing (ELB) appear on the SAA-C03 Exam?
You may be asked to identify the best ELB type for a web application requiring advanced routing based on URL paths and host headers.
A scenario might describe a high-performance gaming application needing to handle a massive number of concurrent TCP connections – determine the appropriate ELB.
Expect questions about troubleshooting scenarios where an ELB is not routing traffic to instances, requiring you to analyze health check configurations and target group settings.
❓ Frequently Asked Questions
When would I choose NLB over ALB?
Choose NLB when you need to handle high throughput TCP/UDP traffic, require static IP addresses, or need extreme performance with minimal latency. ALB is better for HTTP/HTTPS with advanced features.
What is the purpose of listener rules in an ALB?
Listener rules define how the ALB routes requests to different target groups based on conditions like host header, path, or query string. They enable content-based routing and application-level control.
Can an ELB be placed in multiple Availability Zones?
Yes, ELBs are designed to be deployed across multiple Availability Zones for high availability. Distributing them across AZs ensures that your application remains accessible even if one AZ fails.