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When and how to assign a unique identifier for an object in DDD?

A better example would be an object Userthat needs to be saved. I have the following candidates for assigning a unique identifier to a user:

  • Assign keys provided by the back-end (NDB, MySQL, etc.).
  • Manual work with a unique identifier using some service (for example, a system clock).
  • Properties such as emailId.

Taking a simple example of a detailed view, we often have a detailed view of a user of the type some/path/users/{user_id}, if we store emailId as a unique identifier, then there is a chance that the user will one day be able to change his email identifier and it will break.

Which approach is better for identifying the same object?

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2 answers

Named UUID.

UUID, because it gives the identifier a good predictable structure without introducing semantic consequences (for example, an example of your email identifier). Think of a surrogate key .

Named UUID because you want the generated identifier to be deterministic. Deterministic tools play: you can move your system to a test environment and run replay commands to check the results.

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Source: https://habr.com/ru/post/1629492/

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