Almost no one pays attention to 429 for general Web pages. Eg on an RSS file Googlebot speeds up repolling. Amazon RSS feed puller does pay some attention to 429.
503 is at least apparently understood by more crawlers/bots, but they still like to blame the victim: YouTube sends me a condescending (and inaccurate) email when it gets a 503 for ignoring cache headers and other basics it seems...
503 is at least apparently understood by more crawlers/bots, but they still like to blame the victim: YouTube sends me a condescending (and inaccurate) email when it gets a 503 for ignoring cache headers and other basics it seems...