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Is it possible for response times to increase after integrating with Prerender.io?

Yes, briefly. Initial response times can be slower while Prerender.io scans, renders, and caches your site for the first time. Once the cache is warm, you'll see the performance benefits.

TL;DR

Slower response times right after integrating Prerender.io are expected. The first request for any URL is a cache miss, which means Prerender.io renders the page on the fly before serving it (slower). Every subsequent request is a cache hit, served from cache instantly. The slow start is just the cache warming up. You can speed this up by uploading an accurate sitemap, ignoring 404s, and excluding URLs that don't need to reach AI crawlers and search engines. For large sites (50,000+ pages), full cache warming can take days.

 

Why response times look slower at first

When you first integrate Prerender.io, it's normal to see slightly higher response times for a period. This happens because Prerender.io needs to scan, render, and cache every page on your site before the full performance benefit kicks in.

The mechanic is straightforward: the first time any URL is requested through Prerender.io, the page isn't yet in our cache. This is called a cache miss: Prerender.io has to fetch the page from your origin, render it in a headless browser, and only then serve it to the crawler. That takes longer than a cached response. From the second request onward, the page is a cache hit and served from cache instantly.

So early on, when most of your URLs are being touched for the first time, response times naturally skew higher. As more of your site gets cached, the cache hit ratio rises and average response time drops.

 

How to speed up cache warming

  • Upload an accurate sitemap. A sitemap lets Prerender.io discover and cache your URLs proactively rather than waiting for crawlers to request each one. See how to add a sitemap.
  • Ignore 404s. Use the 404 checker to stop Prerender.io from wasting render budget on pages that no longer exist. Pages returning 3xx, 4xx, or 5xx status codes are never cached, so each request to them stays slow forever (and they get removed from cache if they were cached before). See status codes returned by Prerender.io for the full list.
  • Exclude URLs and search parameters that don't need rendering. Use the ignore configuration to filter out non-essential URLs (admin pages, search-result pages with infinite parameter combinations, etc.). Less rendering work means faster cache warming for the URLs that matter.
  • Be patient. For sites with many URLs not in the sitemap, warming the cache can take a while. Prerender.io caches URLs as they're requested by AI crawlers and search engines, so the speed depends on how often each URL is crawled.

 

How site size affects cache warming time

The number of pages on your site is the main factor that determines how long full cache warming takes. For large sites (50,000+ pages), expect cache warming to take multiple days before every URL benefits from instant cache hits. Once the cache is fully warm, you'll see a significant improvement in average response time compared to the initial integration period.

💡 Your daily recache rate scales with your cached page count and your cache expiration setting (roughly NUM_CACHED_PAGES / CACHE_EXPIRATION_IN_DAYS). If you want a faster initial warm-up, upload a sitemap so URLs go through the priority queue. See rendering queues for how the cache-refresh scheduling works.

 

Get support

If it's been several weeks since you activated Prerender.io and response times are still slow, something else may be going on. Contact our support team:

To help us diagnose quickly, please include:

  • The approximate date you activated Prerender.io.
  • Your current cache hit ratio and average crawl time (visible on the dashboard).
  • The total number of URLs in your sitemap (if you have one) vs. the total cached page count.
  • A few example URLs that are still slow after weeks.

 

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💬 Still need help?
If you've been integrated for weeks and your cache hit ratio still isn't climbing, our support team can help dig into your account.
→ Contact us at support@prerender.io

 

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