Amazon CloudFront is a fast content delivery network (CDN) service that securely delivers data, videos, applications, and APIs to customers globally with low latency and high transfer speeds. CloudFront distributions are the core configuration units that define how content is delivered to end users…Amazon CloudFront is a fast content delivery network (CDN) service that securely delivers data, videos, applications, and APIs to customers globally with low latency and high transfer speeds. CloudFront distributions are the core configuration units that define how content is delivered to end users.
A CloudFront distribution specifies the origin servers where your content is stored, such as Amazon S3 buckets, EC2 instances, Elastic Load Balancers, or custom HTTP servers. When users request content, CloudFront routes their requests to the nearest edge location, reducing latency significantly.
There are two types of distributions: Web distributions for static and dynamic content like HTML, CSS, JavaScript, and images; and RTMP distributions (now deprecated) that were used for media streaming.
Key configuration elements include:
- Origins: Define where CloudFront fetches content from. You can configure multiple origins and use origin groups for failover scenarios.
- Cache Behaviors: Control how CloudFront handles requests based on URL path patterns, including TTL settings, HTTP methods allowed, and query string forwarding.
- SSL/TLS Certificates: Enable HTTPS connections using ACM certificates or custom certificates for secure content delivery.
- Geographic Restrictions: Block or allow content access based on viewer locations using geo-restriction settings.
- Price Classes: Control costs by limiting which edge locations serve your content.
- Access Controls: Implement signed URLs or signed cookies to restrict access to private content. Origin Access Control (OAC) secures S3 origins.
For SysOps administrators, monitoring distributions through CloudWatch metrics is essential. Key metrics include request counts, error rates, and cache hit ratios. CloudFront also integrates with AWS WAF for web application firewall protection and provides detailed access logs for troubleshooting.
Invalidations allow you to remove cached objects before their TTL expires, which is crucial during deployments or content updates.
CloudFront Distributions - Complete Guide for AWS SysOps Administrator Associate
Why CloudFront Distributions Are Important
CloudFront distributions are a fundamental component of AWS's content delivery strategy. As a SysOps Administrator, understanding CloudFront is essential because it directly impacts application performance, user experience, and cost optimization. CloudFront reduces latency by caching content at edge locations worldwide, making it critical for serving global audiences efficiently.
What is a CloudFront Distribution?
A CloudFront distribution is a configuration that tells CloudFront how to deliver your content to end users. It defines:
• Origin Settings: Where CloudFront fetches your original content (S3 buckets, EC2 instances, Elastic Load Balancers, or custom HTTP servers) • Cache Behaviors: Rules that determine how CloudFront handles requests for different URL patterns • Distribution Settings: Price class, SSL certificates, geographic restrictions, and logging options
There are two types of distributions: • Web Distribution: For websites, APIs, and HTTP/HTTPS content • RTMP Distribution: For streaming media (now deprecated for new distributions)
How CloudFront Distributions Work
Step 1: User Request When a user requests content, DNS routes the request to the nearest CloudFront edge location based on latency.
Step 2: Cache Check CloudFront checks if the requested content is in the edge cache. If found (cache hit), it serves the content to the user.
Step 3: Origin Fetch If the content is not cached (cache miss), CloudFront forwards the request to the origin server, retrieves the content, caches it at the edge, and delivers it to the user.
Step 4: TTL Management Content remains cached based on Time-To-Live (TTL) settings. You can control TTL using Cache-Control headers or CloudFront settings.
Key Distribution Configuration Components
Origins and Origin Groups: • Origins define where content is fetched from • Origin Groups provide failover capability with primary and secondary origins • Origin Access Identity (OAI) or Origin Access Control (OAC) secures S3 bucket access
Cache Behaviors: • Path patterns determine which requests match each behavior • Viewer protocol policy controls HTTP/HTTPS handling • Allowed HTTP methods specify GET, POST, PUT, DELETE, etc. • Cache key and origin request policies control what is cached
Security Features: • AWS WAF integration for web application firewall protection • Field-level encryption for sensitive data • Signed URLs and signed cookies for private content • Geographic restrictions to block or allow specific countries
SSL/TLS Configuration: • Default CloudFront certificate (*.cloudfront.net) • Custom SSL certificates via AWS Certificate Manager (ACM) - must be in us-east-1 • SNI (Server Name Indication) or dedicated IP for HTTPS
Invalidations and Cache Management
When you need to remove content from edge caches before TTL expiration: • Create invalidation requests specifying file paths • Use wildcards (/*) for bulk invalidations • First 1,000 invalidation paths per month are free • Consider versioned file names as an alternative to invalidations
Monitoring and Troubleshooting
• CloudWatch Metrics: Requests, bytes downloaded/uploaded, error rates, cache hit ratio • Access Logs: Detailed logs stored in S3 for analysis • Real-time Logs: Near real-time log delivery to Kinesis Data Streams • CloudFront Functions and Lambda@Edge: For customizing request/response handling
Exam Tips: Answering Questions on CloudFront Distributions
Origin-Related Questions: • When asked about securing S3 origins, think Origin Access Control (OAC) or Origin Access Identity (OAI) • For high availability scenarios, remember Origin Groups with failover • Custom origins can be any HTTP server with a public DNS name
Performance Questions: • Cache hit ratio improvements involve optimizing cache key settings and TTL values • Price class selection affects which edge locations are used (cost vs. performance trade-off) • Regional edge caches provide an additional caching layer between edge locations and origins
Security Questions: • Signed URLs are for individual file access; signed cookies are for multiple files • Custom SSL certificates must be imported or created in ACM in the us-east-1 region • Geo-restriction uses either CloudFront's built-in feature or third-party geolocation services
Common Exam Scenarios: • Reduce origin load: Increase TTL, optimize cache behaviors, use origin shield • Serve private content: Implement signed URLs or signed cookies with trusted key groups • Improve global performance: Use CloudFront with appropriate price class • Force HTTPS: Set viewer protocol policy to redirect-to-https or https-only • Update cached content: Create invalidation or use versioned file names
Watch for Trick Questions: • CloudFront can cache both static AND dynamic content • Lambda@Edge runs in regional edge caches, not all edge locations • CloudFront Functions are lighter weight than Lambda@Edge but have fewer capabilities • Distribution deployment takes 15-20 minutes to propagate globally
Key Metrics to Remember: • Maximum file size for caching: 30 GB • Default TTL: 24 hours (86,400 seconds) • Minimum TTL can be set to 0 seconds • Maximum TTL: 365 days