AWS Cloud Fundamentals #11: Auto Scaling and Load Balancing

In the previous tutorial, we discussed EC2 instance types and selection within AWS compute services—learning how to choose appropriate EC2 instances based on varying business requirements. This tutorial delves into two other critical compute services: Auto Scaling and Load Balancing. When used together, these capabilities ensure your applications maintain high availability and peak performance under dynamically changing workloads.

Auto Scaling

Auto Scaling is an AWS service that automatically adjusts the number of EC2 instances in response to demand. By defining specific conditions—such as CPU utilization or network traffic—Auto Scaling dynamically adds or removes compute resources, thereby ensuring application availability while optimizing cost efficiency.

How It Works

The core workflow of Auto Scaling operates as follows:

1. Define Scaling Policies: You specify the conditions under which instances should be added or removed—for example, launching one additional instance when average CPU utilization exceeds 70%.
2. Monitor Metrics: Auto Scaling leverages Amazon CloudWatch to continuously monitor instance health and key performance metrics.
3. Automatically Scale Instances: Based on your defined policies, Auto Scaling launches new instances during traffic spikes and terminates surplus instances when demand subsides.

Use Case

Consider an online e-commerce platform experiencing dramatic traffic surges during promotional seasons—but relatively low traffic during off-peak periods. You can configure Auto Scaling with the following policy:

• Scale-out trigger: Add instances when CPU utilization exceeds 80%.
• Scale-in trigger: Remove instances when CPU utilization falls below 30%.

This configuration ensures stable website performance during peak traffic—and cost savings during quieter periods.

Example Code

Below is an example AWS CLI command to create an Auto Scaling group:

aws autoscaling create-auto-scaling-group --auto-scaling-group-name MyAutoScalingGroup \
  --launch-configuration-name MyLaunchConfiguration --min-size 1 --max-size 10 --desired-capacity 2 \
  --vpc-zone-identifier subnet-12345678

Load Balancing

Closely integrated with Auto Scaling is the Load Balancer, which distributes incoming user traffic across multiple EC2 instances—enhancing application availability and operational efficiency.

Types

1. Application Load Balancer (ALB): Optimized for HTTP/HTTPS traffic; supports advanced routing features such as path-based and host-based routing.
2. Network Load Balancer (NLB): Handles TCP and UDP traffic at ultra-high throughput and burst capacity; provides static IP addresses.
3. Classic Load Balancer (CLB): A legacy load balancer with basic functionality, primarily intended for EC2-Classic environments.

How It Works

When a load balancer is deployed alongside an Auto Scaling group, it automatically routes traffic only to healthy, registered instances—whether newly launched or pre-existing—ensuring even distribution and consistent responsiveness.

Use Case

Continuing with the e-commerce platform example, you can configure an Application Load Balancer to distribute all HTTP requests across multiple web server instances. Even during sudden traffic spikes, the load balancer maintains predictable, low-latency response times.

Example Code

Here’s an example AWS CLI command to create an Application Load Balancer:

aws elbv2 create-load-balancer --name MyLoadBalancer \
  --subnets subnet-12345678 subnet-87654321 --security-groups sg-12345678

Combining Auto Scaling and Load Balancing

In practice, Auto Scaling and load balancers are almost always deployed together. During high-load periods, Auto Scaling increases instance count—and the load balancer seamlessly distributes traffic across all active, healthy instances. As a result, your application delivers optimal performance and user experience regardless of traffic fluctuations.

Summary

Through this tutorial, you’ve learned about AWS Auto Scaling and Load Balancing, how they operate, and why they’re indispensable for modern cloud-native applications. Together, these services empower you to handle variable traffic patterns effortlessly—while maximizing resource utilization and minimizing operational overhead.

In the next tutorial, we’ll explore container services—EC2 and ECS—to show you how to deploy, manage, and orchestrate containerized applications on AWS. Stay tuned for more!