Each peer maintains a digital ledger, which contains a record of all committed transactions that a peer has received. The entries in the ledger are stored as key/value pairs. Updates to the same key will replace the current value of a key with a new value. The old value, of course, will stay in the ledger. To provide efficient querying of the latest value of a key, a node can store the latest value of each key in a database such as CouchDB. This database is referred to as a world state in Hyperledger Fabric.
Note that a peer will only receive blocks to commit to its ledger from the channels that it participates in.
A peer can be part of zero or more channels— the channels are not shown in the preceding diagram showing Hyperledge Fabric architecture.