Lately i'm experiencing performance trouble caused by bot traffic. Although Googlebot is not the worst (it's mainly bingbot and ahrefsbot), they cause heavy server load from time to time. We run a lot of sites on one server, so heavy traffic on one site impacts other site's performance.
Problem is that 1) I want a centrally managed solution for all sites (per site administration takes too much time), which 2) takes into account total server-load in stead of only 1 site's traffic and 3) controls overall bot-traffic in stead of controlling traffic for one bot. IMO user-traffic should always be prioritized higher than bot-traffic.
I tried "Crawl-delay:" in robots.txt, but Googlebot doesn't support that. Although my custom CMS system has a solution to centrally manage Robots.txt for all sites at once, it is read by bots per site and per bot, so it doesn't solve 2) and 3).
I also tried controlling crawl-speed through Google Webmaster Tools, which works, but again it only controls Googlebot (and not other bots) and is administered per site. No solution to all three of my problems.
Now i came up with a custom-coded solution to dynamically serve 503 http status codes to a certain portion of the bot traffic. What traffic-portion for which bots can be dynamically (runtime) calculated from total server load at that certain moment. So if a bot makes too much requests within a certain period (or whatever other coded rule i'll invent), some requests will be answered with a 503 while others will get content and a 200.
Remaining question is: Will dynamically serving 503's have a negative impact on SEO? OK, it will delay indexing speed/latency, but slow server-response-times do in fact have a negative impact on the ranking, which is even worse than indexing-latency.
I'm curious about your expert's opinions...
