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AWS Load Balancing vs AWS Auto Scaling Vs AWS Elastic Load Balancing


AWS Load Balancing Vs AWS Auto Scaling
Both AWS Load Balancing and AWS Auto Scaling are incredibly useful services for building highly available and scalable applications on the cloud. While they may sound similar, they actually address different aspects of your infrastructure:

AWS Load Balancing:

  • Distributes incoming traffic: Acts as a traffic cop, directing incoming requests to healthy instances behind the scenes. This ensures no single instance becomes overloaded and improves application responsiveness.
  • Offers high availability: Spreads traffic across multiple Availability Zones (AZs), ensuring your application remains accessible even if an AZ experiences issues.
  • Multiple types: Comes in different flavors like Application Load Balancer (ALB) for handling HTTP/HTTPS traffic, Network Load Balancer (NLB) for low-latency TCP/UDP applications, and Gateway Load Balancer (GLB) for directing traffic to internal services.


AWS Auto Scaling:

  • Automatically scales EC2 instances: Adjusts the number of running instances in an Auto Scaling Group based on predefined metrics like CPU utilization or incoming traffic. This keeps costs optimized and avoids running idle instances.
  • Scales up and down: Can react to traffic spikes by launching new instances and handle lulls by terminating unused ones. This ensures your application always has enough resources but avoids wasting money.
  • Flexible scaling policies: Allows you to define your own scaling thresholds and triggers, giving you fine-grained control over how your application scales.


In short:

  • Load Balancing focuses on distributing traffic and improving availability.
  • Auto Scaling focuses on adjusting the number of instances based on demand.


They work best together:

  • Attach an Elastic Load Balancer to your Auto Scaling Group: This ensures incoming traffic is automatically distributed across your scaled instances.

  • Use CloudWatch metrics to trigger scaling: CloudWatch monitors your instances and sends data to Auto Scaling, which then uses it to scale based on your defined policies.



  • Load Balancing alone won't scale your application. If you have only one instance, even with a load balancer, your application will still experience bottlenecks during peak traffic.
  • Auto Scaling alone won't distribute traffic or improve availability. You need a load balancer to direct traffic to your scaled instances and ensure redundancy.


AWS Load Balancing Vs  AWS Elastic Load Balancing (ELB)
AWS Load Balancing and AWS Elastic Load Balancing (ELB) are two different services, although their names might suggest otherwise. Here's a breakdown of the key differences:


AWS Load Balancing:

  • Legacy service: It's the older of the two and is gradually being phased out by AWS.
  • Limited functionality: Only supports basic Layer 4 load balancing (distributing traffic based on TCP/UDP ports).
  • Less flexible: Offers fewer configuration options and customization compared to ELB.


AWS Elastic Load Balancing (ELB):

  • Modern service: It's the newer and more powerful option, replacing AWS Load Balancing in most cases.

  • Wider functionality: Supports both Layer 4 and Layer 7 load balancing (distributing traffic based on URL paths, headers, etc.).
  • More flexible: Offers a wider range of configuration options and customization, including multiple load balancer types like Application Load Balancers, Network Load Balancers, and Gateway Load Balancers.
  • Scalability: ELB automatically scales to handle increased traffic, while AWS Load Balancing requires manual scaling.


Here's an analogy to illustrate the difference:

  • Imagine AWS Load Balancing as a simple traffic light at a basic intersection. It can direct traffic based on which lane is open, but it doesn't have the intelligence to handle complex traffic patterns or prioritize specific vehicles.

  • AWS Elastic Load Balancing (ELB) is like a modern adaptive traffic management system. It can not only direct traffic based on lanes but also consider factors like congestion, road closures, and even the types of vehicles (e.g., emergency vehicles) to optimize traffic flow and ensure everyone reaches their destination efficiently.


In short, AWS Load Balancing is a basic, legacy service best suited for simple applications with predictable traffic patterns. AWS Elastic Load Balancing (ELB) is the more powerful and versatile option for modern applications requiring flexibility, scalability, and advanced traffic management features.