Why Are Pages Discovered but Not Indexed Despite a 100 PageSpeed Score?

A PageSpeed score of 100 does not necessarily mean Googlebot is experiencing a fast server response. PageSpeed Insights reports Lighthouse lab results and, when available, real user CrUX data. Its Performance score is a weighted combination of performance audits, not a direct measurement of Googlebot crawl performance.

Google Search Console average response time is a different measurement. Crawl Stats reports Google experience when crawling your site. A high response time can indicate that the server is taking longer to respond to Googlebot requests, even when an individual URL performs very well in PageSpeed Insights.

An 884 ms average response time is worth investigating. It is not the sole cause of "Discovered, currently not indexed", but it is one of the major causes. Google determines crawl budget using both crawl capacity and crawl demand. Google says that if a site becomes slower, including increased latency or longer response times/TTFB, its crawl capacity limit can decrease and Google may reduce crawling.

How Server Response Time Affects Crawling

• Google evaluates the site crawling health, including response time and TTFB.
• If response times remain stable or improve, Google crawl capacity limit can increase.
• If the site becomes slower, or returns server errors such as 5xx or rate limiting responses such as 429, Google crawl capacity can decrease.
• A lower crawl capacity can mean Google crawls fewer URLs during a given period.
• However, crawling and indexing are separate processes. A URL being discovered does not guarantee that it will be crawled or indexed, and slow response time alone does not explain every "Discovered, currently not indexed" URL.

What to Investigate

1. Investigate why the server response time is high, especially TTFB and latency.
2. Check server side processing, database queries, application performance, and caching.
3. Use HTTP caching where appropriate. Google specifically recommends supporting 304 Not Modified responses when content has not changed, because this can save server bandwidth and resources.
4. Check for 5xx errors, 429 responses, timeouts, DNS/network problems, and other availability issues.
5. Compare GSC Crawl Stats with your server logs rather than using a single PageSpeed test as evidence of Googlebot crawling performance.
6. For "Discovered, currently not indexed", also investigate Google indexing signals and the quality, uniqueness, internal linking, canonicalization, and overall demand for those URLs. Crawl speed is only one part of the picture.

Key takeaway: a perfect PageSpeed score does not guarantee fast Googlebot crawling, and an 884 ms GSC average response time is a legitimate server performance signal worth investigating. It is one of the major causes of "Discovered, currently not indexed", though not the sole cause. It is not correct to say that 884 ms automatically causes crawl budget to shrink, but slow crawling does reduce how many URLs Google can process. Google describes crawl budget as a combination of crawl capacity and crawl demand, while indexing is a separate evaluation after crawling.