A core promise of the cloud is elasticity, which is the ability to automatically scale resources to meet changing demand. AWS Autoscaling is the service that delivers on this promise, ensuring your application can handle any amount of traffic and remain fault-tolerant.
To achieve true elasticity, AWS Autoscaling works with two other key services: Load Balancers and DNS (Amazon Route 53).
Load Balancers
Load balancers distribute incoming application traffic across multiple targets, such as EC2 instances. They are essential for fault tolerance and high availability.
- Health Checks: Load balancers continuously check the health of the instances associated with them. If an instance is found to be unhealthy (e.g., it fails to respond), the load balancer stops sending traffic to that server and reroutes it to healthy instances.
- Types: AWS offers various types, including Application Load Balancers (ALB) that operate at the application layer to distribute HTTP/HTTPS traffic.
AWS Autoscaling Groups (ASG)
An AWS Autoscaling Group (ASG) is a feature of EC2 designed for dynamic scaling. Its main function is to automatically add (scale out) or remove (scale in) EC2 instances based on demand.
- Scaling Mechanism: The ASG uses metrics (like CPU utilization) monitored by services like CloudWatch to trigger scaling events. This ensures the application maintains performance during traffic spikes and saves money when demand is low.
- Capacity Definitions: When configuring an AWS Autoscaling Group, you define its size:
- Minimum Capacity: The lowest number of servers to run, even during zero load.
- Maximum Capacity: The upper limit of servers the ASG can launch.
- Desired Capacity: The number of servers launched when the ASG is first created.
- Fault Tolerance: By deploying instances across multiple Availability Zones (a Multi-AZ approach), the AWS Autoscaling Group provides high availability. If an instance fails in one AZ, the ASG automatically launches a replacement in a healthy AZ.
- Integration: Load balancers and AWS Autoscaling Groups work directly together. The ASG ensures there are always enough healthy instances available, and the load balancer distributes user requests evenly across them.
Launch Templates
An AWS Autoscaling Group needs a blueprint to define the configuration of the servers it launches. This blueprint is a Launch Template. The Launch Template acts as a blueprint, specifying the AMI, Instance Type, Key Pair, and storage configuration. This standardizes the environment and simplifies replication.
Global Traffic Management: Amazon Route 53 (DNS)
Amazon Route 53 is a highly available and scalable cloud Domain Name System (DNS) web service. It gives businesses a reliable and cost-effective way to route end users to their internet applications.
- Core Functions:
- Domain Registration: You can register domain names (e.g., azinnovatehub.com).
- DNS Routing: It translates human-readable domain names into the numerical IP addresses (e.g., of your load balancer) that computers use to connect.
- Health Checking: It checks the health of your resources by sending automated requests.
- Route 53 Routing Policies: Route 53 uses different routing policies to determine how to answer DNS queries:
- Simple Routing: The standard policy, used to route traffic to a single resource.
- Failover Routing: Reroutes traffic away from resources that have failed health checks. This helps identify and bypass infrastructure or application-level failures.
- Weighted Routing: Routes traffic to multiple resources in specified proportions (e.g., 80% to an old version, 20% to a new version). This is useful for load balancing and testing new software.
- Latency Based Routing: Routes end users to the AWS endpoint that provides the best (lowest) latency for them, improving user experiencing.
Related Service: Content Delivery Network (CDN)
To speed up content delivery globally, providers use Content Delivery Networks (CDNs) like AWS CloudFront. CDNs cache content (like websites and videos) on global “Edge Servers” or “Points of Presence (POPs)” that are geographically close to end users. Data is then delivered from the server nearest to the user, minimizing latency and handling traffic spikes efficiently.
Conclusion: Building a Resilient, Elastic Application
This is where all the pieces come together. You are no longer just building a single server; you are building a resilient, self-healing, and elastic application.
You now know how Load Balancers distribute traffic and perform health checks, while AWS Autoscaling Groups (ASGs) automatically add or remove servers to meet demand. We also covered how Amazon Route 53 (DNS) directs your users to the right endpoint using various routing policies.
You have mastered the core infrastructure. The next step is to explore the powerful managed services that let you move beyond infrastructure and focus on data and code, starting with databases and serverless computing with AWS Lambda.
