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Learn the differences between horizontal and vertical scaling in AWS, how they work, their advantages and disadvantages, and when to use each approach.
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As applications grow, they need more resources to handle increasing traffic and workloads. AWS provides multiple ways to scale applications efficiently.
The two most common scaling strategies are Horizontal Scaling and Vertical Scaling.
Understanding the difference between them is important for AWS certifications, interviews, and real-world cloud architecture design.
Scaling means increasing or decreasing resources to meet application demand.
The goal is to maintain performance while handling more users, requests, or data.
Vertical Scaling means increasing the resources of a single server.
For example:
Upgrade from t3.micro to t3.large
Increase CPU
Increase RAM
Increase storage
Instead of adding more servers, you make the existing server more powerful.
Suppose your EC2 instance has:
2 vCPUs
4 GB RAM
After vertical scaling:
8 vCPUs
16 GB RAM
The application still runs on one server, but with more resources.
Simple to implement
No architecture changes required
Good for small applications
Hardware limits exist
Usually requires downtime
Single point of failure remains
Horizontal Scaling means adding more servers instead of increasing the size of one server.
For example:
Instead of one EC2 instance:
EC2 Instance 1
EC2 Instance 2
EC2 Instance 3
Traffic is distributed across multiple servers using a Load Balancer.
An e-commerce website receives increased traffic during a sale.
AWS Auto Scaling automatically launches additional EC2 instances to handle the load.
High availability
Better fault tolerance
No single point of failure
Supports massive workloads
More complex architecture
Requires load balancing
Application must support distributed workloads
Common AWS services used:
EC2 Auto Scaling Groups
Elastic Load Balancer (ELB)
Application Load Balancer (ALB)
Example:
User Requests ↓ Load Balancer ↓ EC2-1 EC2-2 EC2-3
Traffic is distributed automatically.
Example:
EC2 t3.micro ↓ Upgrade ↓ EC2 t3.large
Same server, more power.
| Feature | Vertical Scaling | Horizontal Scaling |
|---|---|---|
| Method | Increase server size | Add more servers |
| Downtime | Usually required | Usually not required |
| Cost | Higher server cost | More servers |
| Availability | Lower | Higher |
| Fault Tolerance | Low | High |
| AWS Example | Upgrade EC2 instance | Auto Scaling Group |
Netflix serves millions of users worldwide.
Instead of running one large server, Netflix uses horizontal scaling with thousands of servers distributed across multiple regions.
This provides high availability and reliability.
Use Vertical Scaling when:
Small applications
Databases requiring larger resources
Simple workloads
Use Horizontal Scaling when:
High traffic applications
Production systems
Cloud-native architectures
Highly available systems
Q: Which scaling approach is preferred in AWS?
A: Horizontal Scaling is generally preferred because it provides better availability, fault tolerance, and scalability.
Vertical Scaling increases the size of a single server, while Horizontal Scaling adds more servers to handle demand. In modern cloud environments, AWS commonly uses Horizontal Scaling with Auto Scaling Groups and Load Balancers to achieve high availability and scalability.
