Jetpants is an automation toolkit for handling monstrously large MySQL database topologies. It is geared towards common operational tasks like cloning slaves, rebalancing shards, and performing master promotions. It features a command suite for easy use by operations staff, though it's also a full Ruby library for use in developing custom migration scripts and database automation. Jetpants supports a range-based sharding scheme for MySQL by providing a fast way to split shards that are approaching capacity or I/O limitations. Jetpants is able to accomplish this without any locking, downtime, data inconsistency, or query failures. Dynamically resizable range-based sharding allows you to scale MySQL horizontally in a sane manner, without any need for a central lookup service or massive pre-allocation of tiny shards.