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In e-commerce platforms or SaaS services, using AWS CloudFront as a Content Delivery Network (CDN) can effectively reduce latency and improve loading speeds. However, CloudFront Data Transfer Out (DTO) is also one of the main cost items on AWS bills. Many enterprises default to 8TB CloudFront DTO per month when planning AWS budgets, but is this setting sufficient for actual needs? How can we reduce AWS costs through optimized caching strategies, request frequency, and architectural design?
This article will delve into CloudFront DTO calculation methods and provide cost optimization recommendations to make your AWS operations more efficient.
1. Key Factors Affecting CloudFront DTO Transfer Volume
CloudFront DTO mainly comes from the following factors:
- Static resource transfers (images, CSS, JS, videos)
- Dynamic API responses (JSON/GraphQL from frontend-API interactions)
- Page load request counts (PV, Page Views)
- Cache Hit Ratio (CHR)
- Extra traffic during promotional campaigns (such as Double 11, Black Friday)
Therefore, we need to consider user behavior and caching strategies to accurately estimate whether 8TB CloudFront is sufficient.
2. Is 8TB CloudFront Transfer Volume Enough?
(A) Average Data Transfer Per User
Based on typical e-commerce platform structures, a single user browsing the application may generate the following data:
- Homepage (1.5MB)
- Product page (2MB)
- Checkout process (2.5MB)
- Campaign pages (2MB)
- Other small requests (API, recommended products, etc.) (0.5MB)
Single complete browsing session (approximately 5-10 pages):
- Average 10MB / visitor / session
- Daily Active Users (DAU): approximately 10-15% of MAU
- Assume each user averages 1.5 browsing sessions per day
(B) Monthly Transfer Volume Estimation
| Load Level | Estimated Active Users | Daily Active Users (10%-15%) | Daily Total Traffic (GB) | Monthly Total Traffic (TB) |
|---|---|---|---|---|
| Normal Month (30-40%) | 85,000 – 114,000 | 8,500 – 11,400 | 85 – 114 GB | ~ 7.9 TB |
| Regular Promotion (50-60%) | 142,000 – 171,000 | 14,200 – 17,100 | 142 – 171 GB | ~ 12 TB |
| Seasonal Peak (70-80%) | 200,000 – 228,000 | 20,000 – 22,800 | 200 – 228 GB | ~ 16 TB |
| Annual Peak (100%) | 285,000 | 28,500 | 285 GB | ~ 22 TB |
Conclusion: 8TB is reasonable for normal months (30-40% load), but promotional or peak periods may require 12-22TB to meet demand.
3. How to Improve CloudFront Performance and Reduce Costs?
(A) Increase Cache Hit Ratio (CHR) to Reduce DTO Costs
- Cache static resources (JS, CSS, images, videos)
- Use Cache-Control settings for long-term caching
- For API requests, leverage CloudFront + Lambda@Edge for dynamic caching
(B) Impact of CHR Improvement on DTO Costs
| CHR (Cache Hit Ratio) | CloudFront DTO (Monthly Transfer) | S3 Origin Traffic | AWS Cost Impact |
|---|---|---|---|
| 50% | 8TB | 8TB | Higher |
| 60% (Default) | 8TB | 5.33TB | Moderate |
| 80% | 5TB | 2TB | Lower |
Conclusion: Improving CloudFront caching strategy (CHR to 80%) can reduce CloudFront DTO costs by 30-40%.
4. AWS Cost Optimization Recommendations
- Optimize CloudFront caching strategy, increase CHR to 80%
- Use AWS Cost Explorer to monitor CloudFront DTO and predict peak period expansion needs
- For promotional campaigns, dynamically adjust CloudFront configuration to ensure user experience
- Consider AWS Global Accelerator or Cloudflare to reduce DTO costs
5. Conclusion: Is CloudFront 8TB the Best Choice?
Conclusion: 8TB is a reasonable starting configuration, but promotional or peak periods require consideration of expansion to 12TB or more.
- During normal months (30-40% load), 8TB CloudFront DTO can support 85,000 – 114,000 active users with 10-15% DAU.
- During promotions and peak periods (50-100% load), CloudFront may need 12-22TB, otherwise origin costs will increase.
- Cache optimization (CHR to 80%) can reduce CloudFront DTO to 5-6TB, cutting costs by 30-40%.
- Continuous monitoring with AWS Cost Explorer is needed to adjust CloudFront configuration in response to traffic changes.
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