What patterns in server logs indicate inefficient crawling?

• high request volume to parameter URLs;
• excessive redirect chains;
• repeated requests to obsolete URLs;
• large numbers of soft-404-like responses;
• repeated server errors;
• unnecessary URL variants;
• excessive crawling of low-value filters;
• inefficient cache behavior.

A 404 response itself is not automatically evidence of wasted crawl budget. Google's documentation notes that normal 4xx responses generally don't consume crawl budget in the same way as successful responses; 429 is an important exception.

Focus on patterns and consequences rather than treating every non-200 response as a problem.