In the last week, I've had this issue twice. The first time, it self-resolved within a couple of hours. The second time, it just happened, so it hasn't self-resolved yet.

In both instances, when I try to install packages with apt-get, I get 404 errors on mirrorredirect.raspbian.org URLs. Here is a log:

Err http://mirrordirector.raspbian.org/raspbian/ jessie/main mysql-common all 5.5.57-0 deb8u1

404 Not Found [IP: 93.93.128.193 80] Err http://mirrordirector.raspbian.org/raspbian/ jessie/main libmysqlclient18 armhf 5.5.57-0 deb8u1 404 Not Found [IP: 93.93.128.193 80] Err http://mirrordirector.raspbian.org/raspbian/ jessie/main mysql-server-core-5.5 armhf 5.5.57-0 deb8u1 404 Not Found [IP: 93.93.128.193 80] E: Failed to fetch http://mirrordirector.raspbian.org/raspbian/pool/main/m/mysql-5.5/mysql-common_5.5.57-0 deb8u1_all.deb 404 Not Found [IP: 93.93.128.193 80]

E: Failed to fetch http://mirrordirector.raspbian.org/raspbian/pool/main/m/mysql-5.5/libmysqlclient18_5.5.57-0 deb8u1_armhf.deb  404  Not Found [IP: 93.93.128.193 80]

E: Failed to fetch http://mirrordirector.raspbian.org/raspbian/pool/main/m/mysql-5.5/mysql-server-core-5.5_5.5.57-0 deb8u1_armhf.deb  404  Not Found [IP: 93.93.128.193 80]

E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?