If they're hashes, sure. If you want to answer range requests -- e.g. "give me everything starting with ABCDEF" -- you may have a less densely utilized address space (rather like IP networking has had).
My accounting database has keys of the form "usage/"<256-bit user ID><20-byte timestamp><64-bit machine ID><usage type string>. Not 255 bytes, to be sure, but not trivially short either.
If they're hashes, sure. If you want to answer range requests -- e.g. "give me everything starting with ABCDEF" -- you may have a less densely utilized address space (rather like IP networking has had).
My accounting database has keys of the form "usage/"<256-bit user ID><20-byte timestamp><64-bit machine ID><usage type string>. Not 255 bytes, to be sure, but not trivially short either.