# Design a Configurable Order Validator with DAG Dependencies Design an `OrderValidator` whose rules check prohibited items, price ranges, and future conditions. Rules can be added or removed without code changes and may depend on other rules in a DAG. Removing a rule connects each predecessor to each successor while preserving an acyclic valid evaluation graph. ### Constraints & Assumptions - Rule definitions are stored as validated data, such as JSON. - Evaluation must report failures and configuration errors separately. ### Clarifying Questions to Ask - Do all prerequisites need to pass before a rule runs? - What happens if rewiring creates a cycle? ### What a Strong Answer Covers - Schema, safe operators, DAG validation, topological execution, and versioning. - Atomic add/remove operations and testability. ### Follow-up Questions - How would rule rollouts be audited? - How would expensive independent rules run concurrently?