Who/what/how is the keeper of karma?

I have seen multiple references to karma on this site, varying in its descriptions dependent on the question. Most answers appear to have the same answer e.g. Whereas Karma is what happens as a result of your actions or your choices. - Source If karma is the result of my actions or choices and it has a bearing on one's life now and in the next, who/what is the keeper of such actions and choices? Another way to ask the question is how is a record of my actions maintained and kept?