📖 What is AWS Application Load Balancer (ALB)?
AWS Application Load Balancer (ALB) is a Layer 7 load balancer that distributes incoming HTTP and HTTPS traffic across multiple targets, such as EC2 instances or containers. It provides advanced routing capabilities based on path, host, or query string parameters to optimize application performance and reliability.
"Remember that ALB is the go-to choice for microservices and container-based apps because it can route traffic to specific target groups based on the URL path."
📚 Certification: AWS Certified Solutions Architect - Associate (SAA-C03)
🔑 What are the Key Concepts of AWS Application Load Balancer (ALB)?
- ▸ Operates at Layer 7 of the OSI model, enabling intelligent routing based on HTTP headers, URL paths, and hostnames for flexible traffic management.
- ▸ Utilizes Target Groups to organize backend resources like EC2 instances, containers, or Lambda functions, each with its own specific health check settings.
- ▸ Supports Path-based and Host-based routing, allowing a single load balancer to direct traffic to multiple different microservices based on the request URL.
- ▸ Integrates seamlessly with AWS WAF to protect applications from common web exploits and bots by filtering traffic before it reaches the backend.
- ▸ Provides SSL/TLS termination at the load balancer level, reducing the computational overhead on backend servers by handling decryption and encryption.
🎯 How does AWS Application Load Balancer (ALB) appear on the SAA-C03 Exam?
You may be asked to design a microservices architecture where requests to /api and /images must be routed to different sets of EC2 instances; ALB is the correct choice here.
A scenario might describe a need for high-performance, low-latency traffic at Layer 4; you must distinguish why ALB is inappropriate and a Network Load Balancer is required instead.
Expect questions about implementing session persistence using sticky sessions to ensure a user's requests are consistently routed to the same backend instance during a session.
❓ Frequently Asked Questions
What is the main difference between ALB and NLB for the SAA-C03 exam?
ALB operates at Layer 7 (Application) and is best for HTTP/HTTPS traffic with complex routing. NLB operates at Layer 4 (Transport) for ultra-low latency, TCP/UDP traffic, and static IP requirements.
Can an ALB route traffic to a serverless backend?
Yes, ALB can route traffic to AWS Lambda functions. This allows you to build serverless APIs that benefit from load balancing and integrated health checks without managing servers.
How does ALB handle SSL certificates?
ALB integrates with AWS Certificate Manager (ACM) to manage and deploy SSL certificates. It performs SSL termination, meaning the encrypted connection ends at the ALB, and traffic to the backend is typically HTTP.