Usage metering is crucial for companies offering usage-based pricing, enabling accurate billing, cost management, and Product-Led Growth strategies. It involves tracking and recording the consumption of resources or services over time. Implementing an effective metering system requires balancing accuracy, auditability, real-time processing, and cost. Event-based metering is preferred for its accuracy and auditability, while challenges include scaling databases, handling complex stream processing, and avoiding pitfalls like pre-aggregating data.