Elastic Load Balancing

Distribute network traffic to improve the scalability of your applications

Elastic Load Balancing automatically distributes incoming application traffic across multiple targets, such as Amazon EC2 instances, containers, IP addresses, Lambda functions, and virtual appliances. It can handle the varying load of your application traffic in a single Availability Zone or across multiple Availability Zones. Elastic Load Balancing offers four types of load balancers that all feature the high availability, automatic scaling, and robust security necessary to make your applications fault tolerant.

AWS re:Invent 2019: Get the most from Elastic Load Balancing for different workloads (53:59)

Application Load Balancer

Application Load Balancer is best suited for load balancing of HTTP and HTTPS traffic and provides advanced request routing targeted at the delivery of modern application architectures, including microservices and containers. Application Load Balancer routes traffic to targets within Amazon VPC based on the content of the request.

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Network Load Balancer

Network Load Balancer is best suited for load balancing of Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and Transport Layer Security (TLS) traffic where extreme performance is required. Network Load Balancer routes traffic to targets within Amazon VPC and is capable of handling millions of requests per second while maintaining ultra-low latencies.

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Gateway Load Balancer

Gateway Load Balancer makes it easy to deploy, scale, and run third-party virtual networking appliances. Providing load balancing and auto scaling for fleets of third-party appliances, Gateway Load Balancer is transparent to the source and destination of traffic. This capability makes it well suited for working with third-party appliances for security, network analytics, and other use cases.

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Classic Load Balancer

Classic Load Balancer provides basic load balancing across multiple Amazon EC2 instances and operates at both the request level and the connection level. Classic Load Balancer is intended for applications that were built within the EC2-Classic network.

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Highly availability and elasticity

Elastic Load Balancing is part of the AWS network, with native awareness of failure boundaries like AZs to keep your applications available across a region, without requiring Global Server Load Balancing (GSLB). ELB is also a fully managed service, meaning you can focus on delivering applications and not installing fleets of load balancers. Capacity is automatically added and removed based on the utilization of the underlying application servers.


Elastic Load Balancing works with Amazon Virtual Private Cloud (VPC) to provide robust security features, including integrated certificate management, user-authentication, and SSL/TLS decryption. Together, they give you the flexibility to centrally manage TLS settings and offload CPU intensive workloads from your applications. ALB also supports integration with AWS WAF, adding a level of protection before bad actors reach the application. Further, S2N and HTTP Guardian have been developed as Open Source solutions to reduce the potential for HTTP-based attacks.

Feature breadth

Elastic Load Balancing offers the breadth of features needed by businesses of all sizes, while delivering them in an AWS-native experience. Elastic Load Balancing includes support for features needed in container-based workloads, including HTTP/2, gRPC, TLS offload, advanced rule-based routing, and integration with container services as an ingress controller. ALB provides customers with a native HTTP endpoint for calling Lambda functions, removing the dependency on other solutions. Further, Gateway Load Balancer creates one gateway for routing traffic through fleets of third-party appliances.

Robust monitoring & visibility

Elastic Load Balancing allows you to monitor the health of your applications and their performance in real time with Amazon CloudWatch metrics, logging, and request tracing. This improves visibility into the behavior of your applications, uncovering issues and identifying performance bottlenecks in your application stack. ELB helps ensure compliance with application Service Level Agreements (SLAs).

Integration and global reach

As a native AWS service, ELB is tightly integrated with other AWS services like EC2, ECS/EKS, Global Accelerator and operational tools such as AWS CloudFormation and AWS Billing. Across the Amazon Global Infrastructure and customer data centers with AWS Outposts and on-premises target support, ELB is available everywhere you run your AWS workloads.

Use cases

Migrating to AWS

ELB supports the load balancing capabilities critical for you to migrate to AWS. ELB is well positioned to load balance both traditional as well as cloud native applications with auto scaling capabilities that eliminate the guess work in capacity planning. ELB is easy to configure and use, which makes your migration experience simple. The managed experience of ELB means that you can focus on the most critical part of a successful migration - migrating applications - instead of configuring load balancers. ELB also integrates well with the common management tools that you are familiar with such as Terraform and Ansible.

Modernizing applications with serverless and containers

Organizations need to build applications faster than ever, with a combination of modular architecture patterns, serverless operational models, and agile developer processes. ELB adapts to these modern applications and their changing load without customer intervention, scaling out while still only charging for usage. Customers building serverless applications using Lambda can leverage ALB to provide a native HTTP-based endpoint, without requiring complex configurations or using an API gateway. ELB also includes support for containers and container orchestration using Kubernetes, providing load balancing between clients and applications as well as service to service communication.

Building a hybrid cloud

Elastic Load Balancing offers the ability to load balance across AWS and on-premises resources, using a single load balancer. You can achieve this by registering all of your resources to the same target group and associating the target group with a load balancer. Alternatively, you can use DNS-based weighted load balancing across AWS and on-premises resources across two load balancers, with one load balancer for AWS and another for on-premises resources.

Scaling third-party virtual appliances

When migrating to the cloud, some customers look to retain their existing appliances, and the skills and processes they have built around them. Using Gateway Load Balancer, customers deploy appliances from their preferred vendor while taking advantage of the scale and flexibility of running in the cloud.



Qred is a FinTech scale-up that specializes in digital financing solutions for small businesses. In March 2020, the Financial Times named Qred Sweden's fastest growing company and one of the 10 fastest growing companies in Europe.

At Qred, we strongly value our partnership with AWS and the services they provide. Application Load Balancer (ALB) is one of the core pieces of our infrastructure, which we utilize to provide industry-leading cloud solutions to our customers. We have multiple ALB’s integrated with Fargate containers to ensure availability and scalability of our machine learning (QSA) Qred Scoring Algorithm. The algorithm allows us to offer the fastest fintech response times in the Nordics and increasingly across Europe and Latin America.”

Oliver Dolan - CTO, Qred


PayU is one of India's leading payments and fintech companies. PayU serves 4,50,000+ merchants with over 100+ payment methods and is the preferred payment partner for e-commerce merchants, including all leading e-commerce companies and a majority of airline businesses.

“AWS Application Load Balancers’ feature HTTP header based routing enabled us to meet the requirements during peak seasons to ensure the best customer experience. With Application Load Balancers, we can scale our services 10x, meeting peak demand for apps running on EC2.”

Neeraj S Chauhan - Chief Information Officer, PayU


Dream11 is India’s largest fantasy sports platform, with more than 100 million users. The platform is the flagship brand of Dream Sports, India’s leading sports technology company, which also has brands such as FanCode, DreamX, DreamPay, and DreamSetGo as part of its portfolio.

“At Dream11, we leverage Application Load Balancers and Classic Load Balancers for all of the ingress traffic to our fantasy sports platform. We use 100+ load balancers processing more than 65 billion requests per day across all of our microservices ensuring high availability and scalability for our traffic needs.”

Vipin Chaudhary - Director SRE, Dream11


Code.org is a nonprofit dedicated to expanding access to computer science in schools and increasing participation by women and underrepresented minorities. Its annual Hour of Code event aims to engage students in coding and computer science.

“For most students, the Hour of Code™ is their first opportunity to program a computer. This experience needs to be fast and flawless for Code.org to achieve its mission to reach and engage underserved classrooms. Application Load Balancer is critical to the success of the event, ensuring high availability, scalability, and elasticity as traffic increases 400% the morning the event starts.”

Marina Taylor - VP of Product, Code.org


Blog posts and articles

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New – Advanced Request Routing for AWS Application Load Balancers
by Jeff Barr 
March 27, 2019

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