Why We Switched CDNs: How Google's Core Web Vitals Led Us to Cloudflare Pages

This technical SEO case study demonstrates how resolving technical issues and optimizing site infrastructure directly impacts organic visibility. The documented approach provides a template for technical optimization initiatives.

Technical Challenge

Technical SEO issues often create invisible barriers to ranking potential. This case study identifies the specific technical challenges addressed, from crawlability issues to performance bottlenecks. Understanding the problem scope helps practitioners diagnose similar issues.

When a CDN switch is the right diagnosis

Infrastructure migrations are expensive and disruptive, so the bar for choosing one should be high. The honest test is simple: break your LCP into the part that happens before the HTML arrives and the part that happens after. If most of the time is spent before the first byte, hosting is your bottleneck and a platform move can pay off. If most of it is spent after, you have a front end problem and no CDN on earth will fix it.

Run this check on a representative URL rather than the homepage. In Chrome DevTools, open the Network panel, click the document request, and read the Timing tab. The value you care about is "Waiting for server response," which is TTFB. Google's rough guidance is that TTFB should sit under 800 milliseconds for a page targeting a good LCP, because LCP has to fit inside 2.5 seconds and the browser cannot start any work until the HTML lands.

You can also read it straight from the command line, which is the faster way to sample several URLs and several regions:

curl -o /dev/null -s -w \
  "dns: %{time_namelookup}s  connect: %{time_connect}s  tls: %{time_appconnect}s  ttfb: %{time_starttransfer}s  total: %{time_total}s\n" \
  https://example.com/a-real-content-page/

Three patterns point at hosting rather than front end code. First, TTFB that scales with distance: fast from your own city, slow from another continent. Second, TTFB that is consistently high everywhere, which usually means the HTML is being rebuilt per request by an application server. Third, a large gap between the first visit and a repeat visit to the same URL, which suggests the origin is doing work that a cache should have absorbed.

Diagnostic Process

Identifying technical issues requires systematic analysis using crawling tools, log file analysis, and Search Console data. This case study documents the diagnostic methodology that uncovered actionable issues. The process itself provides value for practitioners building technical audit capabilities.

Reading the cache, not the marketing

Nearly every site that believes it "already has a CDN" is caching images, CSS and JavaScript at the edge while still sending every HTML request back to the origin. That configuration leaves the entire TTFB problem in place, because the document request is the one on the critical path. The header tells you the truth in one line:

curl -sI https://example.com/a-real-content-page/ | grep -iE 'cf-cache-status|age|cache-control|x-cache|server-timing'

cf-cache-status: DYNAMIC     (HTML is NOT cached at the edge)
cache-control: private, no-store

DYNAMIC or BYPASS means the edge is forwarding to your origin every time. HIT means the edge served it without touching the origin, which is the state you are migrating toward. Run the same check against a static asset and you will usually see HIT there, which is exactly how teams convince themselves the CDN is doing its job.

The most common single cause of BYPASS on a content site is a session or analytics cookie that the CDN treats as a signal of personalized content. On WordPress in particular, a stray cookie set on every visitor will silently disable full page caching for the entire site while the dashboard still reports a healthy cache hit ratio for assets.

For the wider picture of how edge caching interacts with crawling and rendering, see the guide on CDN SEO and edge caching. If you are considering doing logic at the edge rather than just caching, edge SEO with CDN workers covers what is realistic.

Implementation and Solutions

Each identified issue required specific technical solutions implemented within development constraints. The case study details solutions for rendering issues, performance optimization, crawl management, and indexation improvements. Implementation approaches balance ideal solutions with practical constraints.

What actually breaks during a CDN migration

The performance upside of moving to a static edge platform is fairly predictable. The SEO downside is where migrations go wrong, and it is almost always one of the same five items. Put each of these on the pre launch checklist and verify them again within an hour of the cutover.

The preview URL item deserves emphasis because it is specific to this class of platform and did not exist on traditional hosting. Branch deploys are a genuine productivity gain, and they also publish a complete, crawlable duplicate of your site on a hostname you did not choose. If anything links to one, it can be discovered. The fix is a rule at the edge that returns X-Robots-Tag: noindex for any hostname that is not your canonical domain, applied before the first preview goes live rather than after.

Measurable Impact

Technical improvements demonstrate value through measurable outcomes: improved crawl stats, faster indexation, better Core Web Vitals scores, and ultimately improved rankings and traffic. This case study quantifies the impact of technical optimization.

Measuring the migration honestly

Set the baseline before you touch anything, because after the cutover you cannot recreate it. Capture the p75 for LCP and TTFB on your main templates, the cache status distribution, and a crawl of status codes and canonicals. Then expect the following sequence.

• Immediately: TTFB in your own synthetic checks and RUM. This is the number the migration was supposed to move, and if it has not moved within hours, the cache is not configured the way you think it is.
• Within days: your first party field data for LCP on the affected templates.
• Around 28 days: CrUX and Search Console, which aggregate a rolling 28 day window and therefore cannot show a clean before and after any sooner.
• Weeks later, and cautiously: crawl rate changes. Googlebot does adapt its crawl rate to server responsiveness, so a faster origin can earn more crawl over time, but this is a slow secondary effect and easily confused with unrelated changes.

Be disciplined about the counterfactual. A CDN migration usually ships alongside a build system change, a template refresh, or an image pipeline upgrade, and then nobody can say which one produced the result. If you can, cut over the infrastructure alone, hold everything else for two weeks, and take the clean reading. That patience is what turns a migration into a documented case study rather than an anecdote.

For the metric this work targets most directly, the complete LCP guide breaks down the four sub parts of Largest Contentful Paint so you can see exactly how much of it TTFB owns, and the field versus lab data guide explains why your synthetic checks will move weeks before Search Console does.

FAQ

Technical SEO case studies like this one help practitioners understand the tangible value of investing in site infrastructure.

Source: https://electricui.com/blog/switching-to-cloudflare-pages