Complete Deep Dive into Amazon CloudFront: A Practical “Front-End Optimization” Guide with Hands-On Comparison to Cloud CDN (GCP) and Azure Front Door

Introduction (Key Takeaways)

• This article is a long-form guide that puts AWS’s CDN service “Amazon CloudFront” in the spotlight and compares it with GCP’s Cloud CDN and Azure Front Door, while systematically organizing real-world pain points such as caching strategies, security, cost, logging, and integration with other services.
• Amazon CloudFront caches content across edge locations around the world and is a CDN service that delivers static and dynamic content, video, and APIs with low latency.
• GCP’s Cloud CDN leverages the Google global edge network and integrates tightly with HTTP(S) Load Balancing, while Azure Front Door is positioned as a “front-end platform” that unifies CDN + global load balancing + WAF/DDoS protection.
• What truly matters in real-world operations boils down to these five points:
  1. What will you use as the origin? (S3 / ALB / external)
  2. What will you use as cache keys? (path, query, headers, cookies)
  3. Rules for TTL and invalidation
  4. Security boundaries such as WAF, auth, signed URLs/cookies
  5. How to control cost (cache hit ratio, logs, data transfer)
• The intended audience includes web/mobile app developers, front-end/back-end engineers, SREs/infrastructure engineers, video streaming or game operations engineers, security/governance staff, and startup tech leads.
  • In short, any team delivering something over the Internet—static sites, APIs, images/videos, download distribution, etc.—should find this relevant.
• By the end, the goal is for you to gain a “front-end design mindset” centered around CloudFront that you can easily adapt to Cloud CDN and Front Door as well.

1. What Is Amazon CloudFront? The Role of a CDN and the Positioning of the Three Clouds

Amazon CloudFront is a content delivery network (CDN) that caches content at edge locations worldwide and delivers it from the edge closest to the user.
It handles not only static HTML/CSS/JS/images, but also dynamic pages, APIs, video streaming, and file downloads.

The core idea behind CDNs is simple:

• “Slow performance is really about distance and congestion.”
• “Then let’s place copies closer to users and route traffic over faster paths.”

CloudFront builds these “faster paths” using a combination of edge locations, regional edge caches, and the AWS backbone network.

Roughly speaking, here’s how the three major cloud providers position their services:

• CloudFront (AWS):
  • On top of core CDN features, Lambda@Edge / CloudFront Functions provide “edge compute,” and integration with AWS WAF / AWS Shield / ACM / S3 / ALB is extremely powerful.
• Cloud CDN (GCP):
  • A CDN tightly integrated with HTTP(S) Load Balancing. It is designed to take full advantage of the Google global edge network, anycast IPs, and QUIC/HTTP/2.
• Azure Front Door:
  • Positioned as a “front door” service that consolidates CDN + global load balancing + WAF + DDoS protection + rule engine. It integrates naturally with Azure Firewall and Private Link, and works well with enterprise networks.

All of them share the same objective: serve content from the edge, reduce origin load, and improve user experience.

2. Representative Use Cases and Design Considerations

CloudFront has several “standard patterns” per use case, so it’s a good idea to start by understanding those.

2.1 Web Sites and SPAs

• Origin:
  • S3 (for static sites) or ALB / EC2 / ECS / EKS, etc.
• Key points:
  • A classic pattern is short TTL for HTML + cache busting, and long TTL for assets (CSS/JS/images) with hash in filenames.
  • CloudFront Functions or Lambda@Edge make it easy to implement security headers, redirects, A/B testing, and simple authentication at the edge.

2.2 APIs and Dynamic Content

• Origin:
  • API Gateway / ALB / Lambda URL / ECS / EKS, etc.
• Key points:
  • In many cases you use no-store (no caching), but “micro-caching” with short TTLs on responses can reduce both latency and origin load.
  • Carefully design which parts of the request to include in the cache key (HTTP method, headers, query parameters, etc.).

2.3 Images, Video, and Large Files

• Origin:
  • S3 / MediaStore / external origins (on-prem, etc.)
• Key points:
  • Generally use long TTL + versioned URLs.
  • Pay attention to range requests, HTTP/2, compression, and object size to optimize bandwidth efficiency and cost.

2.4 Download Distribution (Games, Software, Patches)

• Characteristics: Traffic often spikes, and peak bandwidth can be very high.
• Key points:
  • Rely on CloudFront’s autoscaling, and use S3 or high-throughput ALB + autoscaling as origins.
  • Signed URLs are typically used for time-limited and IP-restricted downloads.

3. CloudFront Architecture: Distributions and Behaviors

Let’s quickly organize the core building blocks of CloudFront.

3.1 Distributions and Origins

• Distribution:
  • Configuration unit in CloudFront. It manages settings such as domain name (xxxxx.cloudfront.net), certificates, WAF association, log destination, and default behaviors.
• Origin:
  • The actual backend from which CloudFront retrieves content.
  • Examples: S3 buckets, ALBs, EC2 instances, API Gateway, media services, or external HTTP servers.

3.2 Behaviors (Cache Behaviors)

Behaviors define how to handle requests per path pattern.

• Example:
  • /static/* → long TTL, don’t include query strings in cache key
  • /api/* → short TTL or no-cache, include specific headers/queries in cache key
  • /media/* → allow range requests, enable compression, etc.

Within a single distribution, you can combine multiple origins + multiple behaviors and adjust your caching strategy per path.

3.3 Cache Keys and Policies

CloudFront currently uses a combination of “cache policies” and “origin request policies” to define:

• What’s included in cache keys:
  • Path
  • Query strings (all / whitelist / blacklist)
  • Headers
  • Cookies
• What’s forwarded to the origin

Careful design here has a huge impact on cache hit ratio and predictability of behavior.

4. Caching Strategy: Combining TTL, Versioning, and Invalidation

The most common source of operational incidents in CDN setups is caches not updating when you expect—or updating when you don’t. Getting this right from the start makes life much easier.

4.1 Basic TTL Guidelines

• HTML:
  • Often a short TTL (seconds to minutes) or no-cache so that clients always revalidate with the origin.
• Versioned assets (CSS/JS/images):
  • Include hashes or versions in filenames and use long TTLs (days to weeks).
  • Updates are handled simply by changing the URLs, so you don’t need to worry about old CDN caches.
• API responses:
  • Consider micro-caching (several seconds to tens of seconds) depending on data volatility.
  • For highly dynamic data, no-store may be safer.

4.2 Versioning (Filenames, Paths, Queries)

Common patterns include:

• Embedding versions in paths like /static/v123/app.js
• Adding versions via query strings like app.js?v=123

But you must ensure this aligns with whether queries are included in the cache key.
Establish rules such as “assets use versioned paths; APIs use query parameters for conditions” to avoid confusion within the team.

4.3 Invalidation

• Use invalidation when you forgot to version an asset or need to clear caches urgently.
• CloudFront invalidation works per path (e.g., /index.html or /static/*). However, frequent large-scale invalidations can be costly and slow to propagate, so treat them as an exceptional escape hatch, not a primary update mechanism.

5. Security: HTTPS, WAF, Signed URLs, and OAC

CloudFront also plays a critical role as a security boundary.

5.1 HTTPS, Certificates, and TLS Termination

• CloudFront can handle HTTPS for both viewer side (client ⇔ CloudFront) and origin side (CloudFront ⇔ origin).
• Certificates usually come from AWS Certificate Manager (ACM) and are bound to custom domains.
• Terminating TLS at the edge means client encryption is handled by CloudFront, and backends are accessed over secure internal channels.

5.2 AWS WAF and Shield

• CloudFront includes AWS Shield Standard by default, providing protection against L3/L4 DDoS attacks.
• Adding AWS WAF lets you block:
  • Common attack patterns like SQL injection and XSS
  • Bots, IP reputation issues, and rate-based attacks
    at the edge, before they hit your origin.

5.3 Signed URLs and Signed Cookies

• For paid content or internal-only materials:
  • Use signed URLs with time and IP restrictions.
  • Or distribute signed cookies after login.
• Combining these with CloudFront and S3 allows you to build simple but effective access control without additional servers.

5.4 OAC (Origin Access Control) and OAI

• To restrict S3 origins so they’re only accessible via CloudFront, you use:
  • Legacy: Origin Access Identity (OAI)
  • New recommended option: Origin Access Control (OAC)
• With bucket policies that “allow requests from CloudFront only”, you can prevent direct links and bucket listing.

6. Performance Optimization: Protocols, Compression, and Edge Compute

6.1 HTTP/2, HTTP/3, and Keep-Alive

• CloudFront supports HTTP/2 and HTTP/3, which bring multiplexing and header compression to significantly improve perceived performance, especially on mobile networks.
• Connections to the origin are reused (Keep-Alive), reducing the number of TCP handshakes.

6.2 Compression (Gzip/Brotli)

• CloudFront can serve Gzip/Brotli-compressed content to capable clients.
• For text-based content like HTML/CSS/JS/JSON, compression is almost mandatory, as it directly improves bandwidth usage and response times.

6.3 Edge Compute (Lambda@Edge, CloudFront Functions)

• Lambda@Edge:
  • Runs Node.js/Python code at various points in the request/response lifecycle (viewer/origin request/response).
  • Use cases: A/B testing, locale/country-based redirects, custom auth, response rewriting, etc.
• CloudFront Functions:
  • Ultra-lightweight and ultra-fast JavaScript runtime. Perfect for simple header manipulations, redirects, and pre-auth checks.

7. Logging and Observability: A CDN Without Visibility Is Scary

Troubleshooting CloudFront depends heavily on how well logs and metrics are set up.

7.1 Standard Logs and Real-Time Logs

• Standard access logs:
  • Delivered to S3.
  • Capture client IP, path, status code, cache hits/misses, etc.
• Real-time logs:
  • Streamed to Kinesis Data Streams or Firehose.
  • Use when you need near real-time visibility and detection.

7.2 Metrics (CloudWatch)

Typical metrics include:

• Request count
• 4xxErrorRate / 5xxErrorRate
• BytesDownloaded / BytesUploaded
• CacheHitRate

Suggested SLOs:

• Cache hit rate ≥ 80%
• 5xx error rate < 0.1%

Set up alerts when thresholds are breached.

7.3 Log Analysis Patterns

• Query logs in S3 via Athena or OpenSearch to visualize:
  • Which paths are hitting the origin too often
  • Error patterns by country or ISP
• These insights inform improvements to cache strategy and WAF rules.

8. Pricing Model and Cost Optimization

CloudFront pricing is roughly based on:

1. Data transfer (edge → client)
2. Number of requests
3. Specific features such as real-time logs and Function/Lambda@Edge executions

Always check the latest pricing on the official AWS pricing page.

8.1 Cost Optimization Perspectives

• Improve cache hit ratio:
  • Low hit ratios mean you pay for origin transfer + CloudFront requests + CloudFront transfer.
  • Use versioning and appropriate TTLs to avoid unintentional cache misses on every request.
• Origin location:
  • Transfers from AWS origins (S3/ALB, etc.) to CloudFront benefit from preferential pricing.
• Logging granularity and retention:
  • Don’t send everything to real-time logs. Use a mix like standard logs + real-time logs only for critical paths.
• Handling very small objects:
  • Serving huge numbers of tiny files can make request charges more dominant than data transfer. Consider bundling small assets where possible.

9. CloudFront vs Cloud CDN vs Azure Front Door

Let’s compare these three at a high level.

9.1 Architectural and Integration Differences

• CloudFront (AWS)
  • Focused on CDN but integrates deeply with ALB, S3, API Gateway, media services, WAF, and Shield.
  • Strong support for edge compute (Lambda@Edge, CloudFront Functions).
• Cloud CDN (GCP)
  • Operates tightly coupled with HTTP(S) Load Balancing.
  • Designed to make full use of global anycast IPs, QUIC/HTTP/2, and Google’s backbone.
• Azure Front Door
  • A unified global load balancer + CDN + WAF + DDoS protection + rule engine.
  • Strong integration with Azure DNS, Private Link, Azure Firewall, etc.

9.2 Security, WAF, and DDoS

All three offer:

• L3/L4 DDoS protection, WAF integration, bot mitigation, and TLS termination.

Azure Front Door leans more into being a “one-stop perimeter solution” with integrated WAF, bot management, and DDoS protection.

9.3 Which One Should You Choose?

• Primarily on AWS, using S3/ALB/Media, wanting Lambda@Edge and fine-grained cache control
  → CloudFront is the natural choice.
• Primarily on GCP, centered on Cloud Load Balancer, with BigQuery/Logging integration
  → Cloud CDN fits best.
• Primarily on Azure, needing global load balancing + WAF + Private Link + enterprise network integration
  → Azure Front Door.

In multi-cloud setups, a common pattern is to use each cloud’s front service in front of workloads on that cloud and design a global entry point via DNS and routing.

10. Configuration Samples (CloudFront-Centric, Rough Sketches)

Note: These are simplified examples to convey the general idea.

10.1 Creating a Distribution via AWS CLI (Conceptual Image)

aws cloudfront create-distribution \
  --distribution-config file://dist-config.json

{
  "CallerReference": "2025-11-13-001",
  "Comment": "example static site",
  "Enabled": true,
  "Origins": {
    "Quantity": 1,
    "Items": [
      {
        "Id": "s3-origin",
        "DomainName": "my-bucket.s3.ap-northeast-1.amazonaws.com",
        "S3OriginConfig": { "OriginAccessIdentity": "" }
      }
    ]
  },
  "DefaultCacheBehavior": {
    "TargetOriginId": "s3-origin",
    "ViewerProtocolPolicy": "redirect-to-https",
    "AllowedMethods": { "Quantity": 2, "Items": ["GET","HEAD"] },
    "CachePolicyId": "658327ea-f89d-4fab-a63d-7e88639e58f6"  // Example: CachingOptimized
  },
  "PriceClass": "PriceClass_200"
}

10.2 Sample Cache Policy Strategy

• Cache policy for /static/*:
  • TTL: default 1 day, max 7 days
  • Cache key: path + selected query parameters (only v)
  • Headers and cookies: not included
• Cache policy for /api/*:
  • TTL: several seconds to tens of seconds (or 0)
  • Cache key: path + query + key headers (e.g., language)
  • Cookies: session-related cookies are not in the key (handled at origin)

10.3 Simplified Terraform Example (Conceptual)

resource "aws_cloudfront_distribution" "static" {
  enabled             = true
  default_root_object = "index.html"

  origins {
    domain_name = aws_s3_bucket.site.bucket_regional_domain_name
    origin_id   = "s3-origin"
  }

  default_cache_behavior {
    target_origin_id       = "s3-origin"
    viewer_protocol_policy = "redirect-to-https"
    cache_policy_id        = data.aws_cloudfront_cache_policy.caching_optimized.id
  }

  price_class = "PriceClass_200"
}

11. Design Checklist (Things to Decide in the First Week)

1. Type and location of origins
   • S3 or ALB? Which region? Will you use on-prem or another cloud as origin?
2. Path and behavior splits
   • Decide path segments like /static/, /api/, /media/, /admin/ and how to segment behaviors.
3. Cache keys and TTLs
   • Which parts to include (query, headers, cookies), and TTL strategies.
4. Versioning rules
   • Where to represent versions—filename, path, or query parameters.
5. HTTPS and certificates
   • ACM certificates, custom domains, TLS policies.
6. WAF, DDoS, and authentication
   • WAF rules, signed URLs/cookies, IP restrictions, bot defenses.
7. OAC/OAI and bucket policies
   • Ensuring S3 is not directly exposed.
8. Logs and dashboards
   • Scope for standard vs real-time logs, analytics (Athena, dashboards, etc.).
9. SLO/SLI definitions
   • Cache hit ratio, error rates, p95 latency, and corresponding alerts.
10. Cost monitoring
    • Regularly review transfer costs, request counts, and log storage costs.

12. Common Pitfalls and How to Avoid Them

• Caches not updating—or updating too aggressively
  • Cause: vague TTL and versioning rules, mixed Cache-Control/ETag behavior.
  • Fix: Define and document clear TTL policies, and always version static assets.
• Parts of S3 still accessible via direct links
  • Cause: bucket policies left as public-read.
  • Fix: Use OAC/OAI + bucket policies to allow only CloudFront.
• WAF rules blocking valid traffic
  • Cause: insufficient testing before enabling blocking.
  • Fix: Use Count mode → observe → then switch to Block mode in phases.
• Overwhelming amount of logs and high storage/analysis costs
  • Cause: everything logged at full granularity for long retention.
  • Fix: Use fine-grained logging only for critical distributions/paths, and summarize or shorten retention for others.
• Unclear whether errors come from CloudFront or the origin
  • Fix: Build dashboards correlating CloudFront 5xx errors with origin logs, using correlation IDs where possible.

13. Case Studies (By Scenario)

13.1 Modern Web Service with SPA and API

• Architecture:
  • app.example.com → CloudFront → S3 (SPA)
  • /api/* → CloudFront → API Gateway or ALB → ECS/EKS
• Key points:
  • Set short TTL or no-cache for the SPA’s index.html, and long TTL + versioning for assets.
  • For APIs, handle CORS headers and auth headers at the origin, and consider micro-caching on CloudFront.

13.2 Media Site Focused on Images/Video

• Architecture:
  • CloudFront → S3/MediaStore
• Key points:
  • Separate paths by format/resolution (e.g., /img/hd/, /img/webp/) to simplify cache strategy.
  • Offload transcoding to separate batch or media services and keep CloudFront focused purely on delivery.

13.3 Secure Exposure of an Internal Portal

• Architecture:
  • CloudFront + WAF + signed URLs/cookies → S3/ALB
• Key points:
  • Integrate with an internal IdP (Cognito or external) and generate signed cookies only after login.
  • Add extra controls at CloudFront based on country, IP, and User-Agent to realize a more zero-trust-like perimeter.

14. Who Benefits, and How? (“Happy Future” by Role)

• Front-end engineers
  • Become confident in deciding TTL and versioning for assets, and no longer have to fear cache-related incidents on every deployment.
• Back-end/app developers
  • Learn to design what needs to happen at the origin (CORS, auth, logging, API design) with CloudFront in mind, and graduate from the “CDN is a black box” mindset.
• SREs/infrastructure engineers
  • Package CloudFront + WAF + Shield + logging + SLOs into a standard front-end infrastructure template for the organization.
• Security/governance staff
  • Design an auditable Internet boundary using non-public S3, WAF, signed URLs, and private origins.
• Startup tech leads
  • Even with small teams, can build a robust front-end stack with global distribution, DDoS protection, WAF, and log analytics, ready to scale and go global.

15. Three Things You Can Start Today

1. Put CloudFront in front of an existing site/service
   • Start with a single origin such as S3 or ALB and try it with standard cache policies.
2. Create separate behaviors for /static and /api
   • Simply splitting paths and using long TTL + versioning for assets and short TTL or no-cache for APIs already makes your setup much more robust.
3. Build dashboards for access logs and cache hit ratios
   • Use CloudWatch or Athena to visualize which paths hit the cache, which hit the origin, and where errors occur. You’ll quickly discover improvement opportunities.

16. Conclusion: Think of the Front-End as a Set of “Cache + Boundary + Observability”

Looking at CloudFront with Cloud CDN and Azure Front Door in mind, it becomes clear that modern front-end infrastructure is built on three pillars: “CDN, security boundary, and observability.”

• Decide on caching strategies (keys, TTL, versioning).
• Solidify the boundary (HTTPS, WAF, signed URLs/OAC).
• Visualize logs and metrics (hit ratios, errors, latency).

Once you have these three in place, you can reproduce your design approach even if the cloud or tools change.
In the next article, we’ll look at Amazon CloudWatch as a monitoring platform tightly connected to both backends and CDNs, comparing it to Cloud Monitoring (GCP) and Azure Monitor to explore monitoring, metrics, and logging design in a multi-cloud world.

References

• Amazon CloudFront Developer Guide
• Amazon CloudFront Product Page
• Google Cloud CDN Overview
• What is Cloud CDN and how does it work?
• Azure Front Door Overview (Japanese / English)
• What is Azure Front Door? (Explanation article)

Always check the official documentation and pricing pages for the latest specs, limits, and prices.