Add a server variable to limit or restrict the number of statements (or number of operations) per second that the slave SQL thread will execute/perform. MOTIVATION: To restrict the amount of work slave SQL thread is performing (and theoretically the amount of system resources being consumed), for environments where it is acceptable to have the SQL thread lag behind under certain circumstances. One specific (customer) case was a slave machine that also ran apache. Read queries and Apache were the top priority for the machine (so nice/renice were not options), but replication was consuming too many system resources for them to do their jobs effectively. See also WL#3824 Resource Limits.