This topic discusses HCP best practices for for optimizing REST I/O performance.
Small Object I/O - importance of directory distribution
HCP recommends that key names contain a bit of randomness which translates to using different directory names.
Putting all objects into the top directory "/" will pin database operations to a single region on a single node.
Data itself will get distributed, but the database updates will all converge on the same node.
One popular solution is to hash the object name, and create a directory prefix.
Imagine a simple hash that defined two directories called /odd and /even.
For HCP, they might consider a hash prefix , using the last two characters of MD5 of the file name.
This would create 256 directories.