ELB: Elastic Load Balancer — Improving Availability and Scalability of Applications

ELB: Elastic Load Balancer

What is ELB?

ELB, short for Elastic Load Balancer, is a service provided by Amazon Web Services (AWS) that distributes incoming traffic across multiple targets, such as Amazon EC2 instances, containers, IP addresses, or Lambda functions. It helps improve the availability and scalability of applications by automatically distributing traffic and balancing the load.

Types of ELB

There are three types of Elastic Load Balancers offered by AWS:

1. Application Load Balancer (ALB): ALB operates at the application layer (Layer 7) of the OSI model and is ideal for HTTP and HTTPS traffic. It supports advanced routing features, such as content-based routing and path-based routing, making it suitable for modern application architectures.

2. Network Load Balancer (NLB): NLB operates at the transport layer (Layer 4) of the OSI model and is designed to handle high volumes of traffic. It is best suited for TCP, UDP, and TLS traffic. NLB provides ultra-low latency and can handle millions of requests per second, making it suitable for high-performance applications.

3. Classic Load Balancer (CLB): CLB is the original load balancer provided by AWS and supports both Layer 4 and Layer 7 traffic. It is suitable for applications that require simple load balancing without advanced routing features.

Key Features of ELB

1. Automatic Scaling: ELB automatically scales to handle traffic fluctuations and distributes the load evenly across multiple targets, ensuring optimal performance and availability.

2. Health Checks: ELB regularly checks the health of targets and automatically routes traffic only to healthy targets. It can detect and automatically replace unhealthy targets to maintain a high level of availability.

3. SSL/TLS Termination: ELB can offload SSL/TLS encryption and decryption, reducing the workload on backend servers and improving overall performance.

4. Sticky Sessions: ELB supports sticky sessions, allowing it to bind a user’s session to a specific target. This ensures that subsequent requests from the same user are routed to the same target, maintaining session consistency.

5. Security: ELB integrates with AWS Identity and Access Management (IAM) to provide fine-grained access control. It also supports integration with AWS Web Application Firewall (WAF) to protect applications against common web exploits.

How to Use ELB

Using ELB involves the following steps:

1. Create a Load Balancer: Choose the appropriate type of load balancer (ALB, NLB, or CLB) and configure its settings, such as listeners, target groups, and health checks.

2. Configure Routing: Set up routing rules to determine how traffic should be distributed among different targets. This can include content-based routing, path-based routing, or other advanced routing configurations.

3. Register Targets: Add the targets (e.g., EC2 instances, containers) that should receive traffic from the load balancer to the appropriate target group.

4. Test and Monitor: Validate that the load balancer is distributing traffic correctly by testing and monitoring its behavior. Monitor the health of targets and adjust configurations as needed.

5. Scale and Optimize: As traffic patterns change, monitor the load balancer’s performance and scale it up or down accordingly. Optimize the load balancer’s settings to ensure optimal performance and cost efficiency.


Elastic Load Balancer (ELB) is a powerful service provided by AWS that helps distribute traffic across multiple targets, improving the availability and scalability of applications. With its automatic scaling, health checks, and advanced routing capabilities, ELB simplifies the management of application traffic and ensures a consistent user experience. Whether you choose the Application Load Balancer, Network Load Balancer, or Classic Load Balancer, ELB provides the flexibility and features needed to handle various types of traffic and application architectures.

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