CQRS: fundamentals and practice in Elixir

CQRS: fundamentals and practice in Elixir Series: Part 2 of 5 — CQRS and architecture for AI agents. Reading time: ~7 min. In the previous article we saw why CRUD-centric backends bleed under concurrency and AI agents. Here we cover the conceptual solution (CQRS) and practice in Elixir with Queries and Commands. The fundamentals of responsibility segregation (CQRS) To go beyond the limits of traditional architectures, software engineering turns to CQRS (Command Query Responsibility Segregation). The concept derives primarily from the Command Query Separation (CQS) principle, coined by Bertrand Meyer in 1988 in the context of the object-oriented language Eiffel. CQS states that a function should either change system state (a command) or return a value (a query), but never both. The CQRS pattern, popularized by Greg Young in the context of enterprise systems and Domain-Driven Design (DDD), elevates this principle from individual objects to the macro architecture. CQRS splits the logical