AWS Route 53: Weighted Routing Policy

Overview

The Weighted Routing Policy in Amazon Route 53 allows traffic distribution across multiple resources based on assigned weights. This provides flexible traffic control, enabling use cases such as load balancing, application testing, and gradual traffic shifting.

How Weighted Routing Works

Each DNS record is assigned a weight.
Route 53 calculates the traffic percentage sent to each record using:

Traffic Percentage=Record Weight∑All Record Weights\text{Traffic Percentage} = \frac{\text{Record Weight}}{\sum \text{All Record Weights}}
Weights do not have to sum to 100; they only define relative traffic distribution.

Example Setup

Consider a setup with three EC2 instances, each in a different AWS region:

EC2 Instance	Region	Weight	Traffic Share
Instance 1	us-east-1	70	70%
Instance 2	eu-central-1	20	20%
Instance 3	ap-southeast-1	10	10%

70% of DNS queries will be resolved to us-east-1.
20% will be directed to eu-central-1.
10% will go to ap-southeast-1.

Configuring Weighted Routing in Route 53

Step 1: Create a New DNS Record

Example: weighted.stephanetheteacher.com
Record type: A Record
Routing Policy: Weighted

Step 2: Add Records with Different Weights

First Record (ap-southeast-1)
- Value: EC2 instance IP in ap-southeast-1
- Weight: 10
- TTL: 3 seconds (for testing; higher in production)
- Record ID: "Southeast"