A use case is a command or a query

The CQS (Command-Query Separation) principle from Chapter 6 - Design Principles says that every operation should be either a command (something that changes the system) or a query (something that returns data from the system), but never both.

Use cases follow this principle. Instead of designing a use case to perform both a command and a query like createAndReturnPost, we'd ensure two separate code paths for writes and reads by designing createPost (the command) and getPostById

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