Load Balancer is a managed service provided by Elastic Load Balancing (ELB) that automatically distributes incoming application traffic across multiple targets (like EC2 instances, containers, IP addresses, Lambda functions, etc.) in one or more Availability Zones. It helps ensure high availability, fault tolerance, and scalability for your applications.
Types of Load Balancers in AWS:
Application Load Balancer(ALB) :
Operates at the application layer (Layer 7).
Ideal for HTTP/HTTPS traffic.
Supports advanced routing features like URL-based routing, host-based routing, and path-based routing.
Supports WebSocket and gRPC protocols.
Network Load Balancer (NLB):
Operates at the transport layer (Layer 4).
Designed for ultra-low latency and high-throughput applications.
Ideal for TCP, UDP, and TLS traffic.
Handles millions of requests per second.
Gateway Load Balancer (GWLB):
Operates at the network layer.
Primarily used for integrating third-party virtual appliances like firewalls, intrusion detection systems, etc.
Allows seamless deployment and scaling of virtual appliances.
Classic Load Balancer (CLB):
Operates at both Layer 4 (transport) and Layer 7 (application).
Legacy load balancer, suitable for basic load balancing needs.
AWS recommends using ALB or NLB for new applications as CLB is considered outdated.
Features of AWS Load Balancers:
Health Checks: Monitors the health of registered targets and stops routing traffic to unhealthy ones.
Auto Scaling Integration: Works seamlessly with Auto Scaling groups to add or remove targets as needed.
Security: Supports SSL/TLS termination, AWS WAF integration, and security group configurations.
Cross-Zone Load Balancing: Distributes traffic evenly across multiple Availability Zones.
Elasticity: Automatically scales to handle varying levels of traffic.
Example Use Case:
For a web application, you can use an Application Load Balancer to distribute HTTP/HTTPS traffic among EC2 instances or containers, ensuring better performance and fault tolerance.
For an IoT application requiring high throughput, a Network Load Balancer can manage millions of TCP connections simultaneously.