Content Delivery Networks
Bit the Chipmunk, AWS Expert published on
Hi there, fellow cloud builders! Bit here — your trusty chipmunk pal scurrying through the caching layers of AWS networking. Today, we’re diving into one of my favorite topics: Amazon CloudFront, the content delivery network (CDN) that keeps your users happy and your latency low.
If you’re studying for the AWS Advanced Networking Specialty exam, you’ll need to know how CloudFront fits into network design — when to use it, how it behaves, and what makes it so fast, secure, and cost-effective.
Let’s crack open the acorn of CloudFront knowledge together! 🌰
🧭 Overview
At a high level, you’ll be tested on your ability to:
- Design efficient, secure, and scalable architectures using CloudFront
- Optimize delivery for static, dynamic, and API-based content
- Integrate CloudFront with different origins like S3, ALB, and API Gateway
- Tune and secure distributions for latency, reliability, and cost
In short: know when CloudFront is the right tool, understand its advantages and limits, and how it interacts with other AWS services like Route 53, WAF, and Shield.
☁️ 1. Core Concepts of Amazon CloudFront
| Concept | What You Need to Know |
|---|---|
| Purpose | A global CDN that caches content close to users, reducing latency and boosting performance. |
| Scope | A global service built on AWS edge locations and Regional Edge Caches (RECs). |
| Origins | Common origins: S3, ALB, EC2, API Gateway — each behaves differently. |
| Protocols | Works at Layer 7 (HTTP/HTTPS) and handles both static and dynamic content. |
| Edge Network | Uses AWS’s private backbone — not the public internet — for fast, reliable routing. |
🧩 2. Design Patterns and Use Cases
a. Static Content Delivery
Pattern: CloudFront → S3 Origin
Key ideas:
- Cache static assets (HTML, JS, images, video) globally.
- Protect your bucket using Origin Access Control (OAC) — replaces OAI.
- Use versioned file names for cache control (e.g.,
style.v3.css). - Add WAF and Shield for DDoS protection at the edge.
Bit’s Tip: If the data rarely changes and must reach users worldwide → CloudFront + S3 is your best nut in the stash.
b. Dynamic or Personalized Content
Pattern: CloudFront → ALB → EC2 (or ECS/EKS services)
Key ideas:
- CloudFront still speeds up connections, even when content isn’t cached.
- Use cache keys or query string filtering to cache partial responses.
- Origin Groups can provide automatic failover.
- Set Minimum TTL = 0 for truly dynamic data.
- Use Lambda@Edge for request rewrites or authentication.
Bit’s Tip: Even “dynamic” doesn’t mean “uncacheable”! CloudFront helps with connection reuse and TLS optimization, too.
c. API Acceleration
Pattern: CloudFront → API Gateway (edge-optimized endpoint)
Key ideas:
- Edge-optimized APIs already include CloudFront under the hood.
- Regional APIs need a custom CloudFront distribution if you want caching.
- Cache GET responses to reduce latency and cost.
- Integrate WAF for extra security.
Bit’s Tip:
- CloudFront = HTTP/HTTPS + caching.
- Global Accelerator = TCP/UDP + static IPs (no caching).
d. Video Streaming and Large Files
Pattern: CloudFront → S3 or MediaPackage
Key ideas:
- Supports HLS, DASH, and CMAF streaming.
- Tune TTLs and cache behavior for frequently watched segments.
- Use signed URLs or cookies for controlled access.
Bit’s Tip: Don’t confuse this with S3 Transfer Acceleration — that’s for uploads, not streaming!
e. Multi-Region Active-Active
Pattern: CloudFront → ALBs in multiple Regions
Key ideas:
- Origin Groups provide region-level failover.
- You can combine CloudFront with Route 53 or Global Accelerator for global balancing.
- Lambda@Edge can route users by geography or custom headers.
Bit’s Tip: CloudFront failover happens at the origin layer, which is faster than waiting for DNS failover.
🔐 3. Security and Access Control
| Feature | Description | Why It Matters |
|---|---|---|
| Origin Access Control (OAC) | Lets only CloudFront reach your S3 bucket. | Commonly tested! Know it well. |
| Signed URLs / Cookies | Time-limited or user-specific access. | Used for paid or private content. |
| Field-Level Encryption | Encrypts sensitive data at the edge. | Rare but worth knowing. |
| AWS WAF Integration | Protects from SQLi and XSS. | Best practice for web security. |
| AWS Shield | DDoS protection (standard = free, advanced = SLA). | Expect at least one exam question on this. |
⚙️ 4. Performance Optimizations
| Feature | What It Does |
|---|---|
| Regional Edge Caches (REC) | Intermediate caches reduce origin load. |
| Cache Behaviors | Configure path-based caching (e.g., /api/*, /images/*). |
| Compression | Gzip/Brotli support for smaller payloads. |
| Persistent Connections | CloudFront reuses TCP/TLS connections. |
| HTTP/2 and HTTP/3 | Faster for modern browsers. |
Bit’s Tip: Even if nothing is cacheable, CloudFront can still help — because it shortens the distance for TCP/TLS handshakes.
💸 5. Cost Optimization
| Strategy | Why It Helps |
|---|---|
| Longer TTLs | Fewer origin requests → lower cost. |
| Price Classes | Use fewer edge locations to save money. |
| CloudFront Functions | Cheaper than Lambda@Edge for simple logic. |
| Limit Invalidations | Beyond 1,000 paths/month, they cost extra. |
Bit’s Tip: On exam day, if you see a trade-off between latency vs. cost, think about price class or TTL adjustments.
🌍 6. Comparing CloudFront with Other Services
| Service | Use Case |
|---|---|
| CloudFront | HTTP/HTTPS delivery, caching, WAF, DDoS, edge logic |
| Global Accelerator | TCP/UDP acceleration with static IPs |
| Route 53 | DNS-based traffic control |
| S3 Transfer Acceleration | Faster S3 uploads only |
Bit’s Tip: Caching or WAF = CloudFront. Static IPs or non-HTTP = Global Accelerator. Routing between regions = Route 53.
🧠 7. Common Exam Scenarios
Scenario 1:
A company delivers static and dynamic web content globally and wants to minimize latency. ✅ CloudFront → ALB → EC2
Scenario 2:
A finance app must share reports securely for 24 hours only. ✅ CloudFront with signed URLs and OAC
Scenario 3:
An API needs global caching and DDoS protection. ✅ CloudFront in front of API Gateway
Scenario 4:
A multiplayer game uses UDP for real-time updates. ❌ CloudFront (HTTP only) ✅ Global Accelerator
And there you have it — a CloudFront crash course straight from the forest floor! 🌲 Keep these patterns and principles in your pouch, and you’ll be ready for anything the ANS-C01 exam tosses your way.
Until next time — stay cached and stay clever! 🐿️