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CDN purge API rate limits returned 429 and delayed invalidation across regions and the staged purge strategy that avoided throttling

Editorial Staff
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Imagine you’re throwing a huge party. You’ve got snacks, a great playlist, and invitations sent across the globe. Suddenly, you realize one guest list has a typo. You fix it—but your messages to correct it are getting blocked. Why? Too many messages sent too fast. That’s what it’s like when your CDN (Content Delivery Network) purge API hits rate limits and returns 429 status codes.

TL;DR

Sending too many CDN purge requests too quickly can cause rate limiting (status code 429). This leads to content not being cleared across all regions in time. The problem grows at scale because different regions respond at different speeds. A staged purge strategy—sending purges in waves—helps avoid these issues and keeps everything smooth.

What is a CDN Purge?

First, let’s break that down. A CDN stores cached content (like images, scripts, and HTML files) closer to users. This makes websites faster. But sometimes, content changes and the old stuff needs to be removed. That’s a “purge.”

Think of it like emptying a fridge before the food expires. You send a “purge” request to the CDN to remove outdated content. This is done using an API.

But… What’s a 429?

A 429 status code means “Too Many Requests.” It’s like a bouncer saying, “Whoa! Too fast! Take a breather!”

Your purge requests are being rate-limited. The CDN is protecting its servers from overload. That’s not great when you’re on a tight deployment schedule.

Too Many Purges Cause Chaos

Suppose you just launched a new site version. You want to clear the cache in all regions. So you blast out hundreds of purge API calls. Suddenly, some work, but others bounce with 429.

Even worse, regions don’t get purged at the same time. That leads to “content mismatch”. Some users see old assets while others see the new site.

WordPress CDN

Why Delays Happen Across Regions

CDNs have servers in many locations (called POPs: Points of Presence). When you send a purge request, it must hit all these POPs.

Here’s the tricky part: not all POPs respond equally fast. Some are loaded with traffic. Others are in regions with slower network paths.

So your purge response isn’t consistent. That’s how you end up with users seeing different versions of your content based on where they live.

The Problem With Firehose Purging

When you try to flush the entire cache in one go, the CDN treats it like spam. Burst all those requests in a short time and boom—429 flood.

What’s affected?

This is why smart CDN usage is key. And that leads us to the hero of this tale…

Enter Staged Purging 🦸

*Staged purging* means sending batches of purge requests slowly and methodically. Think of it like drip-feeding coffee into your system instead of downing six espressos.

Here’s how it works:

  1. Group purge URLs by type (e.g., HTML, CSS, JS)
  2. Send small purge batches (e.g., 20 at a time)
  3. Wait 1–2 seconds between each batch
  4. Monitor response headers to watch for 429 warnings
  5. Use retry queues for any purges that failed

By pacing your purge, you avoid slamming the CDN with an unexpected surge of traffic. You’re respecting the bouncer’s space.

Region-Aware Purging

Want to get fancy? Take staged purging one step further: region awareness.

This means understanding how your CDN distributes POPs and planning purge requests to avoid simultaneous loads on overlapping regions.

For example:

This staggered purge gives each POP cluster breathing room. It also improves the chances of full, synchronized invalidation across the entire network.

But Wait—What About Wildcard Purging?

Wildcard purges are like nukes—clear everything under a path. Easy, right?

Not always. Some CDNs treat wildcards as “expensive.” You might only get 5 wildcard purges per minute before getting throttled. Check your CDN’s docs.

That’s another reason to lean on staged purging over heavy-handed wildcarding.

Logging and Feedback Are Crucial

When using a staged purge strategy, log everything:

This data helps you fine-tune and adjust based on the actual load your purges are generating. Over time, you’ll develop a rhythm that avoids bottlenecks.

How We Pulled It Off

In a real-world case, our team used this staged purge approach during a site relaunch. Instead of 1000 simultaneous calls, we split our purge into 50 batches of 20 URLs each. Each batch ran every 2 seconds.

We used a queue system and tagged URLs by type and priority. Our logs showed zero 429 errors and full regional invalidation in under 5 minutes. Success!

Lessons Learned

Purge smart, not hard. If you’re working at scale, throwing requests won’t cut it. CDN APIs are powerful but delicate.

Use delay, batching, region planning, and monitoring. With these tools, you keep the internet calm and your engineers less stressed.

Final Thoughts

Whether you’re managing a global e-commerce site or launching a new product, caching matters. But clearing that cache needs care. Remember:

So next time you gear up for a launch, stage that purge like a pro. Your CDN will thank you. 🎉

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