s52256 was stressing wikireplicas by creating high-cpu usage on the database. The tool has been rate-limited to avoid creating issues to other users (which complained about lag on IRC).
Please review the queries used or if some changes have to happen (it is not necessarily your fault, it may be due to mediawiki structure changes, that could have made it less efficient; or sometimes, abuse from 3rd parties).
It was also not necesarilly the only cause of issues, but we have to start by the top utilizator, and that was this tool at the time at the issue, going almost back to normal after rate-limiting. Please work on us on figuring out what could be done, app-rate limiting, etc.