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Edge Computing with Cloudflare Workers & Deno · Lesson

Blue-Green & Gradual Rollouts

Deploy edge applications safely using blue-green deployments and gradual traffic rollouts to minimize risk and enable instant rollback.

Blue-Green & Gradual Rollouts is a free Edge Computing with Cloudflare Workers & Deno lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Edge Computing with Cloudflare Workers & Deno learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

The Risk of Big-Bang Deploys

Shipping a new version to 100% of users at once is risky, a hidden bug hits everyone instantly.

Progressive deployment strategies reduce blast radius by exposing changes gradually and enabling fast rollback.

Blue-Green Deployments

In a blue-green setup you run two environments:

  • Blue, the current live version
  • Green, the new version, fully deployed but not yet receiving traffic

You switch traffic to green when ready, and switch back instantly if something breaks.

Gradual (Canary) Rollouts

A gradual rollout sends a small percentage of traffic to the new version first, then increases it as confidence grows.

  • 5% then 25% then 50% then 100%
  • Watch error rates at each step

Also called a canary release.

Versioned Uploads

Cloudflare lets you upload a new Worker version without deploying it to all traffic.

wrangler versions upload
# uploads a new version, 0% traffic by default

Splitting Traffic by Percentage

Use gradual deployments to assign a percentage of requests to each version.

wrangler versions deploy \
  <new-version-id>@10% <old-version-id>@90%

Manual Routing for Control

For custom logic you can route in code, for example send a cohort to the new behavior based on a hash of the user ID.

function inCanary(userId) {
  // simple stable bucketing
  return (userId.charCodeAt(0) % 100) < 10; // ~10%
}

Watch the Right Metrics

During a rollout, monitor:

  • Error rate / 5xx responses
  • Latency (p50, p95, p99)
  • CPU time
  • Business KPIs

Compare the new version against the baseline before increasing traffic.

Instant Rollback

The key benefit of progressive deploys is fast rollback, shift traffic back to the known-good version immediately.

wrangler versions deploy <old-version-id>@100%

Automating Rollback

Tie rollout steps to CI checks. If error rates exceed a threshold, the pipeline automatically reverts to the previous version.

if (errorRate > 0.02) {
  await rollbackToPrevious();
}

Database Compatibility

During blue-green, both versions may run at once, so schema changes must be backward compatible.

  • Add columns before removing old ones
  • Use expand-then-contract migrations

Best Practices Summary

Deploy safely at the edge by:

  • Uploading versions without full deploy
  • Splitting traffic gradually and watching metrics
  • Keeping rollback one command away
  • Making migrations backward compatible

Quick Check

What is the defining characteristic of a canary (gradual) rollout?

Recap

You learned safe deployment strategies:

  • Blue-green keeps a hot standby for instant switching
  • Gradual rollouts shift traffic in steps while you watch metrics
  • Versioned uploads and percentage splits make this easy on Cloudflare
  • Backward-compatible migrations keep both versions healthy

Progressive delivery turns scary deploys into routine, reversible events.

Frequently asked questions

Is the “Blue-Green & Gradual Rollouts” lesson free?

Yes — the full text of “Blue-Green & Gradual Rollouts” is free to read here on the web, and the Edge Computing with Cloudflare Workers & Deno course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Edge Computing with Cloudflare Workers & Deno course, upgrade to CoddyKit PRO.

What will I learn in “Blue-Green & Gradual Rollouts”?

Deploy edge applications safely using blue-green deployments and gradual traffic rollouts to minimize risk and enable instant rollback. You practise Edge Computing with Cloudflare Workers & Deno with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Edge Computing with Cloudflare Workers & Deno?

No prior experience is required. Edge Computing with Cloudflare Workers & Deno on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Blue-Green & Gradual Rollouts” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Edge Computing with Cloudflare Workers & Deno lesson?

Yes. Every Edge Computing with Cloudflare Workers & Deno lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Deno Deploy & CLI
  2. Custom Runtime Environments
  3. Testing & CI/CD for Edge
  4. Blue-Green & Gradual Rollouts
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