CQS vs CQRS

• is Command-Query Responsibility Segregation on a smaller scale
• is a principle of imperative computer programming
• it states that every method should either be a:
  • command - change data
  • query - returns data

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• is Command-Query Separation on a larger scale
• originated with Bertrand Meyer’s Command and Query Separation Principle
• If you have a return value you cannot mutate the state. If you mutate the state your return type must be void

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