When would you use CQRS in a .NET application, and what does it not require?

CQRS: when separate read and write models help

Applies CQRS proportionally, separating model responsibilities without assuming separate databases, messaging, or event sourcing.

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I consider CQRS when writes enforce rich invariants but reads need very different shapes, joins, filtering, or scaling. Commands express intent and return an outcome, while queries return purpose-built read models without mutating state. In a modest application both sides can share one database and transaction technology. That lightweight separation can improve clarity without introducing distributed consistency.

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Command-query separation, read models, write invariants, scaling, consistency, complexity, and event-sourcing misconceptions.

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Why this question matters
CQRS separates models for changing state from models for reading it. It does not automatically require separate services, databases, a message bus, or event sourcing.
I consider CQRS when writes enforce rich invariants but reads need very different shapes, joins, filtering, or scaling. Commands express intent and return an outcome, while queries return purpose-built read models without mutating state. In a modest application both sides can share one database and transaction technology. That lightweight separation can improve clarity without introducing distributed consistency.
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The trade-off appears when read data is projected asynchronously or owned separately. Then clients may see stale results, projection failures need repair, and operations need correlation. I would not add that machinery to simple CRUD. Direct EF Core projections may be enough for reads, while write handlers use domain behavior and focused persistence. Command and query types should describe business operations rather than create a class-per-method framework ritual.

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Saying CQRS requires event sourcing.
Creating command and query classes for trivial CRUD with no benefit.
Ignoring stale reads after asynchronous projection.
Applying authorization only to commands.

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