I don't like the prefix idea: besides the duplication of information, it also becomes a liability if you ever rename things.

Imagine you prefix all customer IDs with `cus_`, but at some point decide to rename Customer to Organization in your codebase (e.g. because it turns out some of the entities you are storing are not actually customers). Now you have some legacy prefix that cannot be changed, is permanently out of sync with the code and will confuse every new developer.