MongoDB Documentation, Release 3.0.4 "shard" : "shard0004" } These documents store the range of values for the shard key that describe the chunk in the min and max fields. Additionally the shard field identifies the shard in the cluster that “owns” the chunk. The config (page 738) database is internal: applications and administrators should not modify or depend upon its content in the course of normal operation. The collections (page 740) collection stores a document for each sharded collection in the cluster. Given a collection named pets in the records database, a document in the collections (page 740) collection would resemble the following: The config (page 738) database is internal: applications and administrators should not modify or depend upon its content in the course of normal operation. The databases (page 740) collection stores a document for each database in the cluster, and tracks if the database has sharding enabled. databases (page 740) represents each database in a distinct document. When a databases have sharding enabled, the primary field holds the name of the primary shard . { "_id" : "admin", "partitioned" : false , "primary" : "config" } { "_id" : "mydb", "partitioned" : true , "primary" : "shard0000" } The config (page 738) database is internal: applications and administrators should not modify or depend upon its content in the course of normal operation. The lockpings (page 740) collection keeps track of the active components in the sharded cluster. Given a cluster with a mongos running on example.com:30000 , the document in the lockpings (page 740) collection would resemble: { "_id" : "example.com:30000:1350047994:16807", "ping" : ISODate( "2012-10-12T18:32:54.892Z" ) } config. lockpings config. databases config. collections Internal MongoDB Metadata Internal MongoDB Metadata { "_id" : "records.pets", "lastmod" : ISODate("1970-01-16T15:00:58.107Z"), "dropped" : false , "key" : { "a" : 1 }, "unique" : false , "lastmodEpoch" : ObjectId("5078407bd58b175c5c225fdc") } Internal MongoDB Metadata Chapter 10. Sharding 740