Comprehensive request logging provides visibility into API usage patterns, performance bottlenecks, and security incidents. I log structured JSON that includes request method, path, parameters (sanitized to exclude passwords), response status, duration, and user context. For production systems, I send logs to a centralized aggregation service like Datadog or CloudWatch where I can query and alert on patterns. The key is balancing detail with noise—I avoid logging full request bodies for performance reasons, instead sampling them at low volume or in staging environments. Request IDs tie together all log entries for a single request, making distributed tracing possible without heavyweight instrumentation.