📖 What is Elastic Load Balancing (ELB)?
Elastic Load Balancing (ELB) automatically distributes incoming application traffic across multiple targets, such as EC2 instances, containers, and IP addresses. This enhances the fault tolerance, scalability, and availability of applications by preventing any single target from becoming a point of failure.
"ELB comes in three types: Application Load Balancer (ALB), Network Load Balancer (NLB), and Classic Load Balancer. Know the use cases for each. The exam will test your understanding of how ELB integrates with Auto Scaling and health checks. Distinguish between layer 4 and layer 7 load balancing."
📚 Certification: AWS Certified Cloud Practitioner (CLF-C02)
🔑 What are the Key Concepts of Elastic Load Balancing (ELB)?
- ▸ ELB distributes traffic across multiple targets, improving application availability and fault tolerance by removing single points of failure.
- ▸ ALB operates at Layer 7 (application layer) and supports HTTP/HTTPS, enabling content-based routing and host-based routing.
- ▸ NLB operates at Layer 4 (transport layer) and is designed for high performance and low latency, ideal for TCP/UDP traffic.
- ▸ Health checks are crucial; ELB monitors target health and only routes traffic to healthy instances, ensuring application reliability.
- ▸ ELB integrates with Auto Scaling groups to automatically adjust capacity based on demand, maintaining optimal performance.
🎯 How does Elastic Load Balancing (ELB) appear on the CLF-C02 Exam?
You may be asked to identify the appropriate ELB type for a web application requiring content-based routing based on URL paths.
A scenario might describe an application experiencing high traffic spikes – expect questions about how ELB and Auto Scaling work together to handle this.
Expect questions about troubleshooting scenarios where an application is unreachable, and you must determine if the ELB health checks are configured correctly.
❓ Frequently Asked Questions
When would I choose NLB over ALB?
Choose NLB when you need extremely high performance, low latency, and are dealing with TCP, UDP, or TLS traffic. ALB is better for HTTP/HTTPS with advanced routing.
What happens if all targets behind an ELB become unhealthy?
If all targets are unhealthy, the ELB will return 502 Bad Gateway errors to clients. Proper health check configuration is vital to minimize downtime.
How does ELB contribute to cost optimization?
By distributing traffic efficiently, ELB allows you to scale your resources only when needed, reducing costs associated with over-provisioning. It also integrates with Auto Scaling.