Elastic Load Balancer Flashcards
What is an Elastic Load Balancer (ELB)?
Elastic Load Balancer (ELB) distributes incoming application or network traffic across multiple targets, such as Amazon EC2 instances, containers, and IP addresses, across one or more Availability Zones.
What are the types of Elastic Load Balancers available in AWS?
The main types of Elastic Load Balancers are Application Load Balancer (ALB), Network Load Balancer (NLB), and Classic Load Balancer (CLB). Each serves different use cases and network/application needs.
How does an Application Load Balancer (ALB) work?
ALB operates at the request level (layer 7), routing traffic to targets within Amazon VPC based on the content of the request. It’s suitable for advanced load balancing of HTTP and HTTPS traffic.
How does a Network Load Balancer (NLB) work?
NLB operates at the connection level (layer 4), routing traffic to targets within Amazon VPC based on IP protocol data. NLB is optimized for high performance, low-latency, and static IP addresses for applications.
How does a Classic Load Balancer (CLB) work?
CLB provides basic load balancing across multiple Amazon EC2 instances and operates at both the request level (layer 7) and connection level (layer 4). CLB is considered a legacy option and is recommended for use with EC2-Classic instances.
What are the key features of ALB?
Key features of ALB include advanced request routing based on the content, support for container-based applications, HTTP/2 and WebSocket protocols, and native IPv6 support.
What are the benefits of using NLB?
NLB offers extreme performance and scalability, the ability to handle millions of requests per second with ultra-low latencies. It’s also capable of handling volatile workloads and preserving the source IP address.
When to choose ALB over NLB or CLB?
Choose ALB for advanced routing needs, HTTP/HTTPS traffic, microservices, and container-based applications requiring path-based routing. ALB is more feature-rich compared to NLB and CLB for application-level traffic.
What is sticky sessions (session affinity) in ELB?
Sticky sessions allow requests from the same client to be routed to the same target, which is useful for ensuring that user sessions are persisted to the same server for web applications.
How can ELB improve the fault tolerance of applications?
ELB improves the fault tolerance of applications by automatically distributing incoming traffic across multiple targets, health checking targets, and only routing to healthy ones. This ensures application availability even if one or more targets fail.
