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Rendering Queues

Understand how Prerender.io prioritizes page recaching and when pages get removed from the cache.

Summary/Overview

Prerender.io uses two rendering queues—priority and normal—to manage how cached pages are refreshed over time. These queues ensure that the most important or time-sensitive content is recached first, while the rest of your pages are handled in the background. This system helps optimize crawl efficiency and rendering performance.

The queues process pages daily based on your cache freshness interval and total number of cached URLs, meaning your recache activity scales intelligently with site size.

Detailed Explanation / How It Works

Recache Rate

Your daily recache rate is calculated by:

NUM_CACHED_PAGES / CACHE_EXPIRATION (in days)

To determine how many pages are recached per hour, simply divide that number by 24. As you cache more pages or lower your cache expiration (TTL), the system ramps up accordingly within your queue allocation.

Priority Queue

The priority queue handles urgent or user-initiated recaches. It includes:

  • URLs submitted via the API
  • Pages listed within your Sitemaps
  • URLs added manually in the Dashboard’s Cache Manager

These pages are recached in order of request, ensuring timely processing for high-priority pages.

Normal Queue

The normal queue is triggered automatically and recaches pages that have exceeded their cache freshness threshold. It starts with the oldest cached pages and works forward in time.

Status Codes and Automatic Cache Removal

If a cached page returns an invalid or problematic status code during recache, Prerender.io automatically removes it from the cache. This ensures your cached pages only include valid and functional responses.

Status codes that trigger cache removal on recache:

  • Status code < 200
  • Status code > 200 and < 304
  • Status code > 304 and < 500
  • Three consecutive responses with status code >= 500

These rules help Prerender maintain a clean and SEO-appropriate cache that doesn’t return broken or temporary redirects to search engines.

Step-by-Step Usage (How Pages Get Recached)

  1. Pages are cached either through bot visits, manual submission, or integrations.
  2. Your daily recache rate is calculated using your total cached page count and cache expiration policy.
  3. The priority queue handles custom recache requests first (e.g., API, Sitemaps).
  4. The normal queue handles older cached pages automatically.
  5. If a page returns an invalid status during recache, it is removed from the cache.

Common Pitfalls / Tips

  • Use meaningful cache expiration values—shorter TTLs mean higher recache frequency,  therefore, higher usage.
  • Too many low-priority URLs in sitemaps can delay important pages—optimize lists accordingly.
  • Unexpected 3xx or 4xx status codes can cause good pages to be removed—test routes for issues.
  • Use the Status Codes guide to optimize server responses.

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