Traffic spikes should feel like a busy day, not an outage. This guide covers CDN basics, cache rules, autoscaling, and load tests for Build Me Web hosting.
CDN basics
Static assets and cacheable HTML ship from the edge close to visitors. Dynamic checkout and account routes bypass cache or use short TTLs with careful cache keying. The goal is to keep origin calm while pages stay fresh enough for your business.
Understand what is safe to cache: fingerprinted JS/CSS/images for long TTL; HTML for public marketing pages with purge-on-publish; never shared-cache authenticated HTML.
- Inventory public vs private routes.
- Enable edge caching for static and approved HTML.
- Configure purge hooks on site publish and deploy.
- Verify
Cache-ControlandVaryheaders on sample URLs.
Hash asset filenames so you can cache “forever” without teaching users to hard-refresh after every deploy.
Cache rules
Fingerprint assets for long TTL. Purge on publish for HTML that must update immediately. Never cache authenticated responses at the shared edge. Be careful with Vary: Cookie — it can fragment cache effectiveness.
# Illustrative policies
/assets/* Cache-Control: public, max-age=31536000, immutable
/blog/* Cache-Control: public, s-maxage=60, stale-while-revalidate=600
/account/* Cache-Control: private, no-storeQuery parameters: ignore harmless ones (fbclid) in cache keys when safe; never ignore parameters that change content.
Autoscaling
Scale compute on CPU and request concurrency. Set floors for known campaigns so cold starts do not coincide with your launch email. Scale down slowly enough to survive traffic ripples without flapping.
Databases and third parties often become the bottleneck before web nodes — include them in capacity planning. Connection pools should match scaled worker counts.
Load tests
Rehearse peak traffic on staging with production-like data volumes. Capture p95 latency, error rates, and saturation metrics before marketing flips the switch. Test read-heavy and write-heavy paths separately.
- CDN purge verified after a content publish
- Authenticated routes confirmed uncached at edge
- Autoscaling floor set for campaign week
- Load test report attached to launch checklist
Troubleshooting
Stale HTML: purge rules missing for that path; check CDN provider logs.
Origin overload: cache hit ratio low — review cache keys and TTLs.
Regional slowness: large unoptimized images or origin fetch on every request for assets that should be edge-cached.
Prerequisites & preparation
Before changing production settings for CDN and scaling, align the people who own content, DNS, analytics, and approvals. A fifteen-minute kickoff that names owners prevents multi-day Slack archaeology later. Capture decisions in the workspace notes so the next teammate inherits context instead of guesswork.
Gather credentials and access: workspace admin or editor role, DNS control when hostnames are involved, payment or API sandbox accounts when money paths are involved, and a shared checklist link. Confirm which environment you will rehearse in — preview first, production only after a green run.
Inventory public vs private routes and list campaigns that need capacity floors.
Detailed walkthrough
Work the happy path slowly the first time. Narrate what you expect to see after each click: a status badge, a DNS record, a webhook delivery, a Lighthouse metric. When reality diverges, stop and resolve the mismatch instead of clicking ahead — most outages begin as ignored yellow states.
- Enable long-TTL caching for fingerprinted assets.
- Set HTML cache/purge policy for marketing pages.
- Confirm authenticated routes are private/no-store at the edge.
- Set autoscaling floors before known peaks.
- Load-test staging with production-like data volumes.
Edge cases & failure modes
Plan for partial failure. Networks drop, registrars delay, providers rate-limit, and humans approve the wrong revision. Your runbook should say what “abort” looks like: leave preview up, roll back the release, or freeze campaigns until metrics recover.
- Cache keys fragmented by junk query params.
- Origin overload from low cache hit ratio.
- Database pool exhaustion when web tier scales without DB plan.
QA checklist before you announce
- Happy path verified on mobile and desktop
- Failure path messaging reviewed
- Owners named for the first hour after launch
- Rollback or freeze path documented
Operating the change
After launch, watch the metrics that prove the change worked — not vanity charts. Pair quantitative signals with one qualitative check (support ticket themes, sales feedback). Schedule a follow-up within a week to remove temporary flags, raise DNS TTLs, or archive the experiment.
Review cache hit ratio and p95 latency after each major campaign.
Treat CDN and scaling as a repeatable playbook. The second time your team runs it should be faster because the checklist and owners already exist.
Hash assets so “cache forever” is safe across deploys.
Never shared-cache HTML that depends on personalization cookies without careful Vary design.
Purge hooks on publish keep editors from blaming “the internet” for stale heroes.
Load tests should separate read-heavy browsing from write-heavy checkout.
Third parties and large images often dominate more than your origin code — profile honestly.
Regional performance issues may be image CDN or DNS related — measure by geography.
Implementation checklist
Confirm fingerprinted assets with long TTL on preview before you promote. Name who approves the change, which environment is authoritative, and what “done” looks like in measurable terms.
Document HTML purge-on-publish hooks where the team already looks — workspace notes or the engineering handbook — not only in a meeting memory.
Operating it with your team
Rehearse private cache rules for authenticated HTML against written acceptance checks. If you cannot name the verification event (order, DNS lookup, deploy health, or signed API call), you are not ready to announce.
Measure ignoring junk query params in cache keys with anonymized but realistic data, and keep logs, headers, or screenshots for at least one release cycle so regressions have a baseline.
When you finish this guide, you should be able to explain the happy path, the abort path, and the metrics that prove success. If any of those are fuzzy, revisit the walkthrough with your teammates before you scale traffic, spend, or automation.