[IanCal]

I have two minor, but useful, uses:

One is that the prefix is probably unique for small sets. So it's both easy to read and parse and then use just a prefix for doing something like stopping a docker container.

Second is that a short prefix on a larger set of data is probably not unique but at a rate I can predict. I can take a random, and repeatable, sample of data by selecting everything with the same prefix. This gives me a fast way of taking a random sample from a database (or file or anything else).