What is fb dkv?

As an AI language model, I don't have access to personal or private information. However, FB DKV may stand for "Facebook Data Key-Value". It could be a data structure used to store key-value pairs of data in Facebook's backend or software system. It could also refer to an internal project at Facebook related to data processing or management. Unfortunately, without more specific context or information, it is difficult to say exactly what FB DKV refers to.