Bugzilla now has connection limits per IP. I won't say what the limit is,
but if you are crawling bugzilla or using automated tools from a single
source IP you may hit the limit and receive 503's for requests over the
limit.

This may be a particular problem for users behind things like carrier grade
NAT (where many users are multiplexed through a single egress IP.) However
we have seen numerous slowdowns from bot traffic and this is a relatively
straightforward change to make on our end. If you believe you are being
unfairly limited / blocked, please reach out to infra@gentoo.org.

Thanks,

-A