mtbl is a C library implementation of the Sorted String Table (SSTable) data structure, based on the SSTable implementation in the open source Google LevelDB library . An SSTable is a file containing an immutable mapping of keys to values. Keys are stored in sorted order, with an index at the end of the file allowing keys to be located quickly. mtbl is not a database library. It does not provide an updateable key-value data store, but rather exposes primitives for creating, searching and merging SSTable files. Unlike databases which use the SSTable data structure internally as part of their data store, management of SSTable files -- creation, merging, deletion, combining of search results from multiple SSTables -- is left to the discretion of the mtbl library user.