What difficulties may arise when using a key to identify objects if it also stores additional information about its content?

If the key for object identification contains not only a unique identifier but also additional information about the content, the following difficulties may arise:

• Violation of the principle of single responsibility of the key. The key should unambiguously identify the object, not carry additional logic or data.
• Performance issues and comparisons. When comparing keys, additional information must be considered, complicating search and sorting operations.
• Errors when changing additional information. If the additional information changes, the key also changes, which can lead to loss of connection with already stored objects.
• Serialization and storage difficulties. Additional data can complicate storing keys in databases or caches.

It is better to separate the identifier from metadata so that the key remains stable and easy to use.