What Is a Query Handler?

A query handler is code that receives a query describing what data is wanted and returns it, performing no writes. It often reads from a denormalized read model tuned for fast retrieval rather than from the write model. Separating it from command handlers lets reads and writes scale and evolve on their own.

Why it matters

Keeping reads side-effect free makes them easy to cache, replicate, and optimize. It cleanly separates the data shape users see from the model used to enforce business rules.

Related guides