Entitlements and billing are intricately linked yet distinct components in the architecture of software services, particularly when it comes to usage-based billing models, as exemplified by Lago's approach. Entitlements refer to features included in a plan and are governed by feature flags, while billable metrics are units for which users are charged. The article discusses the tension between keeping these systems separate to reduce complexity and combining them to simplify user experience and data management. Lago has integrated entitlements directly into its billing system to streamline operations, making it easier for both technical and non-technical users to manage complex plans without creating dependencies or "duct tape code." This integration maintains the simplicity of a single system while preserving the safety and functionality of separate services, addressing challenges posed by evolving AI-driven pricing models and ensuring coherent management of customer access and billing data.