System and method for proactively buffering quantum key distribution (QKD) key material

A system and method are provided for proactively buffering quantum key distribution (QKD) key material. The method includes monitoring key generation rates and surpluses at QKD devices at each node of a QKD link in a QKD network, retrieving surplus key material from the QKD devices at one or both nodes of the QKD link, and buffering the surplus key material in a local storage at one or both nodes in the QKD link. The surplus key material can be used to offset overhead introduced in securely relaying keys between non-adjacent demand pairs in the QKD network. The surplus key material can also be used to offset future transient decreases in key generation rates.