Facebook is the largest photo sharing website in the world. The amount of daily uploaded pictures is at least 300 million per day. The best way to manage this amount of information is filename which is working with an alphanumerical key. Example:
1_holiday.jpg
2_christmas.jpg
2a_christmastree.jpg
2b_Deliciouscake.jpg
2b1_recipeforcake.png
3_sport.jpg
3a_photoofshoes.jpg
The numerical ID for each photo remains the same. It is given once during the creation. New photos can be added to the collection by choosing the id according to the existing system. The files are sorted by its similarity. In the literature the concept is described as hierarchical clustering of images