When building modern, scalable and reliable applications on AWS, one essential service that often goes underappreciated is the AWS Elastic Load Balancer (ELB). Whether you are running web servers, APIs or containerized applications, a load balancer ensures your system stays performant and available even under heavy load.
In this blog, I will break down what an AWS Load Balancer is, how it works, the different types and how to use it effectively to enhance your architecture.
What is an AWS Load Balancer?
An AWS Load Balancer automatically distributes incoming traffic across multiple targets such as EC2 instances, containers, IP addresses and Lambda functions in one or more Availability Zones.
This helps improve fault tolerance, scalability and application performance by preventing any single server from becoming a bottleneck or point of failure.
In simple terms, the AWS Load Balancer acts as the traffic controller for your application directing requests to the best available server.
How Does AWS Load Balancer Work?
Here is what happens when a request hits your AWS Load Balancer:
- Client Request → A user or client sends a request to your application
- DNS Resolution → The request resolves to your Load Balancer’s DNS name (not directly to a specific instance)
- Load Balancer Routing → AWS Load Balancer evaluates which target (EC2 instance, container etc.) is healthiest and least loaded
- Forwarding the Request → The Load Balancer forwards the traffic to the selected target
- Response to Client → The target processes the request and sends the response back to the client via the Load Balancer
This process ensures seamless performance, high availability and even distribution of traffic.
Types of AWS Load Balancers
AWS offers three main types of load balancers, each serving different use cases:
1. Application Load Balancer (ALB)
- Operates at the Application Layer (Layer 7)
- Best suited for HTTP and HTTPS traffic
- Supports advanced routing features such as:
- Path-based routing (
/api,/login) - Host-based routing (
api.example.com,app.example.com) - Redirects, fixed responses and WebSocket connections.
- Path-based routing (
- Ideal for microservices and containerized applications (ECS, EKS).
Use Case: Routing REST APIs or web app traffic between multiple services.
2. Network Load Balancer (NLB)
- Operates at the Transport Layer (Layer 4)
- Handles TCP, UDP, and TLS traffic
- Extremely fast capable of handling millions of requests per second
- Provides static IP addresses and ultra low latency
Use Case: Real-time gaming, financial transactions or systems needing extreme performance.
3. Gateway Load Balancer (GLB)
- Operates at Layer 3 (Network Layer)
- Designed to distribute traffic to third-party virtual appliances like firewalls, intrusion detection systems and deep packet inspection tools
- Simplifies the deployment of security and monitoring appliances
Use Case: Deploying network security and monitoring solutions at scale.
Why Use AWS Load Balancer?
Here are some major benefits of using a Load Balancer in your AWS architecture:
| Feature | Description |
|---|---|
| High Availability | Distributes traffic across multiple Availability Zones |
| Auto Scaling Support | Works seamlessly with Auto Scaling groups |
| Security Integration | Integrated with AWS Certificate Manager (ACM) for SSL/TLS |
| Health Checks | Automatically removes unhealthy instances |
| Seamless Failover | Redirects traffic in case of instance or zone failure |
| Cost Efficiency | Pay-as-you-go pricing only pay for usage |
How to Set Up an AWS Load Balancer
You can easily create a Load Balancer via the AWS Management Console, AWS CLI or Infrastructure as Code (IaC) tools like Terraform or CloudFormation.
Using the AWS Console:
- Go to the EC2 Dashboard → Load Balancers
- Click Create Load Balancer
- Choose the type (Application, Network or Gateway)
- Configure:
- Listeners (protocol and port)
- Target Groups (EC2 instances or containers)
- Health Checks
- Review and Create the Load Balancer
Once it is live, AWS automatically assigns a DNS name that you can use to access your application.
Pro Tips for Optimizing AWS Load Balancers
- Use HTTPS (SSL/TLS) termination at the Load Balancer level for better security
- Combine Auto Scaling Groups with ALB for automatic capacity adjustment
- Monitor performance using Amazon CloudWatch
- Use sticky sessions for applications that require session persistence
- Enable cross-zone load balancing to evenly distribute traffic across zones
Real-World Example
Let’s say you run an e-commerce website hosted on three EC2 instances. During a flash sale, thousands of users hit your site simultaneously.
Without a Load Balancer, one instance could crash due to overload.
With an Application Load Balancer, AWS automatically routes traffic to the healthiest instances and scales up or down based on demand ensuring a smooth shopping experience for your customers.
When Should You Use an AWS Load Balancer?
Use AWS Load Balancer when:
- Your application runs on multiple EC2 instances
- You want to ensure zero downtime during deployments
- You are using microservices or containers (ECS/EKS)
- You want automatic failover and high availability
- You need secure HTTPS routing with SSL certificates
AWS Load Balancer Pricing
AWS Load Balancer pricing is based on:
- Load Balancer hours (uptime)
- Data processed (GB)
- New connections and active flows
You can estimate your cost using the AWS Pricing Calculator
Conclusion
AWS Load Balancer is a powerful and essential component of modern cloud architectures. It enhances performance, availability and scalability ensuring that your users always experience a smooth and reliable service.
Whether you are hosting a small web app or a large-scale enterprise system integrating an AWS Load Balancer is a must for achieving true cloud resilience.
Key Takeaways
- Load Balancers distribute traffic evenly across multiple targets
- Choose ALB for HTTP/HTTPS, NLB for high-performance TCP/UDP, and GLB for network-level appliances
- Combine it with Auto Scaling, CloudWatch, and SSL for optimal performance
- AWS ELB is your gateway to highly available, secure, and scalable cloud infrastructure
Author
Khaled Md Saifullah
Full Stack Developer | AWS Enthusiast | Open Source Contributor
- GitHub: km-saifullah
- LinkedIn: Khaled Md Saifullah
Tags
#AWS #CloudComputing #DevOps #LoadBalancer #WebDevelopment #MERN #Scalability #HighAvailability
Top comments (0)