Amazon Cloudfront

🔗 Quicklinks (Bookmark):

Amazon CloudFront is AWS’s global CDN for accelerating web apps, APIs, and media with 700+ points of presence and built-in DDoS protection (Shield Standard). It’s fast—but bills can spike from data transfer out, request volume, edge compute (Functions/Lambda@Edge), invalidations, and over-broad geography. This page blends Grok’s outline with a pragmatic FinOps playbook, including Security Savings Bundle details.

🚀 What is CloudFront?

CloudFront securely delivers static/dynamic content, video, software, and APIs with low latency from a global edge network. It integrates tightly with S3, ALB/EC2/ECS, and media origins—origin→CloudFront transfer from AWS origins is $0/GB—and supports edge compute for request/response customization.

Features

  • Global edge network with intelligent routing and caching

  • Edge compute: CloudFront Functions (ultra-light JS) and Lambda@Edge (full Node.js)

  • Built-in security: AWS Shield Standard at no extra cost; WAF/Shield Advanced optional

  • HTTPS by default; signed URLs/cookies, Origin Access Control (OAC/OAI), field-level encryption

  • Free tier for low/steady workloads

Common content types

  • Static/dynamic web, API traffic, streaming/live/on-demand video, downloads/game updates/firmware, IoT data

⚙️ Price Classes — pick the right coverage

Class
Coverage
Use when

All

Full global network (700+ PoPs)

Truly global audiences and latency-sensitive media

200

Broad global, excludes some higher-cost/remote regions

Balanced cost/performance for worldwide but concentrated audiences

100

Major markets (NA/EU plus select regions)

Cost-focused when most users are in North America/Europe

Start with the narrowest Price Class that meets your latency SLOs; expand only where data shows a need.

🧬 Edge compute options

Option
Best for
Notes

CloudFront Functions

Header/cookie rewrites, URL normalization, simple auth/AB tests

Sub-ms, ultra-low cost; no network calls/body access; runs at edge location

Lambda@Edge

Complex logic: body transforms, origin selection, external calls

Higher cost & latency; code replicated globally; runs at regional edge cache

Rule of thumb: Prefer Functions for simple logic; use Lambda@Edge only when you need body/network access.

🏛️ Origins & deployment

Origin
Use when
Notes

S3

Static sites/assets/downloads

Pair with OAC; origin fetches to CloudFront are free

ALB/EC2/ECS/EKS

Dynamic sites, APIs, personalized content

Cache what you can; still benefits from free origin→edge transfer

MediaPackage/MediaStore

Live/VOD streaming

Segment-friendly caching; consider Origin Shield for origin offload

All distributions support HTTPS; enable field-level encryption for sensitive headers.

🧠 CloudFront optimization strategy

Quick wins

  • Put CloudFront in front of AWS origins to zero out origin→edge transfer

  • Choose the lowest Price Class that meets user latency

  • Prefer CloudFront Functions over Lambda@Edge for light logic

Caching & behaviors

  • Long TTLs for immutable assets; use cache policies to vary only on required headers/cookies/query params

  • Enable Brotli/Gzip compression; use Origin Shield to reduce origin hits

  • Design path-based behaviors (e.g., /api/* vs /static/*) and apply appropriate TTLs

Traffic control & security

  • Geo-restrict regions you don’t serve; block obvious abuse with AWS WAF

  • Use signed URLs/cookies for private content; keep S3 buckets private via OAC/OAI

Invalidations & housekeeping

  • Batch invalidations (the first 1,000 paths/month are free); avoid wildcard nukes

  • Target >80% cache hit ratio; analyze top URLs, regions, and status codes monthly

💸 Pricing model & the Security Savings Bundle

Plan
What you pay for
Notes

Pay-as-you-go

Data transfer out (tiered by geo), HTTP/HTTPS requests, optional features (real-time logs, FLE), edge compute invocations

Baseline pricing for most workloads

Free Tier

1 TB data out + 10M HTTP/HTTPS requests + 2M CloudFront Functions invocations/month

Great for dev/low-volume

CloudFront Security Savings Bundle

Commit to a monthly CloudFront spend for 12 months and get up to ~30% savings across CloudFront usage types. Includes AWS WAF usage credits up to ~10% of your monthly commit.

Self-service signup; your regular usage draws down the commit; overages billed at standard rates. Shield Advanced not included

Bundle cheat-sheet

  • Term: 12 months; billed on a monthly spend commitment

  • Applies to: Data transfer out, requests, Functions, Lambda@Edge, logging, etc.

  • Security kicker: WAF credits (up to ~10% of your commit) included

  • Good fit when: Your CloudFront spend is predictable/stable month-to-month

📊 Cost controls to turn on

  • Geo reports + Price Class to align coverage with audience demand

  • Cache hit ratio monitoring; fix low-hit paths with cache keys/TTLs

  • Budgets/alerts for DTO spikes, invalidation overages, and edge compute invocations

  • Real-time logs for hot-path debugging and bot analysis

🔒 Security & compliance

  • Shield Standard is included; layer AWS WAF for app rules (bot control, rate limiting, OWASP)

  • OAC keeps S3 private; use mTLS/signed URLs/cookies for private delivery

  • Field-level encryption for sensitive headers; log delivery to S3 with lifecycle rules

📈 Monitoring & tools

  • CloudWatch: Requests, BytesDownloaded, 4xx/5xx, CacheHitRate

  • CloudFront reports: popular objects, geos, user agents, origin metrics

  • Real-time logs: near-instant request detail for analysis (deliver to Kinesis/Data Firehose)

  • Cost Explorer/CUR: break down DTO by region tier, requests, Functions/Lambda@Edge

🧪 Practical selection cheat-sheet

  • Mostly NA/EU traffic → Start Price Class 100; expand only where latency proves it

  • Simple header/URL logic → CloudFront Functions

  • Complex body/origin logic → Lambda@Edge (with guardrails)

  • Video/media → Pair with MediaPackage/Origin Shield, tune segment caching

  • API behind ALB → Use cache policies to vary on auth headers minimally; enable compression

✅ CloudFront FinOps Checklist

🧠 AWS CloudFront Cost Optimization Challenges

CloudFront is “cheap” until request volume, DTO to expensive geos, invalidations, and edge compute sneak up on you. Here are the non-trivial traps teams hit—and fixes that actually move the needle.

Q1: We used Price Class All by default. Are we overpaying?

Many workloads don’t need every edge location. Serving from high-cost regions inflates DTO.

✅ Solution

  • Start with Price Class 100 (NA/EU) or 200; expand only where latency data requires it.

  • Track p95 latency and CacheHitRate by country/region before widening coverage.

Q2: Our Data Transfer Out (DTO) is huge—and we’re unsure about origin egress.

Viewer DTO is unavoidable, but origin→edge behavior differs by origin type.

✅ Solution

  • Front AWS origins (S3/ALB/EC2) with CloudFront to eliminate origin→edge transfer.

  • Compress (Brotli/Gzip), minimize payloads, and increase TTLs to reduce bytes delivered.

  • If using non-AWS origins, model & monitor that origin’s egress cost explicitly.

Q3: Deploys cause invalidation storms.

Frequent invalidations add up after the monthly free tier and can degrade cache efficiency.

✅ Solution

  • Use content-hashed filenames for static assets so you rarely invalidate.

  • Batch invalidations and avoid /*. Keep under the free 1,000 paths/month when possible.

Q4: Lambda@Edge is getting expensive.

Running heavy logic at the edge across all requests drives compute and duration costs.

✅ Solution

  • Move simple logic (URL/header/cookie rewrites, A/B flags) to CloudFront Functions.

  • Keep Lambda@Edge only for use-cases needing body access, network calls, or complex transforms.

  • Consolidate event hooks (e.g., viewer-request vs origin-response) to reduce invocations.

Q5: Our Cache Hit Ratio (CHR) is stuck ~60%.

Over-varying cache keys and short TTLs cause misses and extra origin load.

✅ Solution

  • Tighten cache keys: vary only on required headers/cookies/query parameters.

  • Use long TTLs for immutable assets; verify Cache-Control vs min/max TTLs.

  • Add Origin Shield to reduce miss fan-out and improve hit locality.

Q6: Real-time logs quietly added dollars.

Per-line billing (plus streaming/processing) adds up if left on all the time.

✅ Solution

  • Enable real-time logs only during targeted debug windows or with sampling.

  • Use standard logs/metrics for day-to-day; add budgets/alerts on log volume.

Q7: Our origin melts even with CloudFront in front.

Low CHR, many behaviors, or globally distributed demand can overwhelm origins.

✅ Solution

  • Enable Origin Shield and pick a shield Region close to your origin.

  • Normalize cache keys; raise TTLs on cachable routes; validate ETags/conditional GETs.

  • Re-examine behavior split (/static/* vs /api/*) to maximize caching.

Q8: “Our API is personalized, so we can’t cache.” Any savings left?

Treating APIs as fully uncacheable leaves DTO and request charges untouched.

✅ Solution

  • Cache fragments: public endpoints, metadata, per-user blocks with short TTLs.

  • Keep vary lists tight (e.g., a single auth header/cookie) to avoid cache explosion.

  • Compress responses and minimize payloads to reduce DTO even on misses.

Q9: We have predictable traffic—are we missing a bigger discount?

Teams on steady spend often leave list-price money on the table.

✅ Solution

  • Enroll in the CloudFront Security Savings Bundle: 12-month monthly commit for CDN savings, plus WAF credits.

  • Commit at a level you consistently hit; avoid over-committing if traffic is volatile.

  • Re-size the commit at renewal based on actuals.

Q10: If we raise CHR, will CloudFront cost automatically drop?

Higher CHR reduces origin load, but CloudFront still bills viewer DTO/requests.

✅ Solution

  • Reduce bytes delivered (compression, image formats/sizing) and expensive regions (Price Class).

  • Reduce request counts via longer TTLs and better caching on semi-static routes.

  • Use reports to correlate hot paths with cost and adjust behaviors accordingly.

📚 Reference

Features and pricing change; validate specifics for your Region in AWS pricing/docs before rollout.

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