The document discusses distributed tracing at Pinterest. It provides an overview of distributed tracing, describes the motivation and architecture of Pinterest's tracing system called PinTrace, and discusses challenges faced and lessons learned. PinTrace collects trace data from services using instrumentation and sends it to a collector via a Kafka pipeline. This allows PinTrace to provide insights into request flows and performance bottlenecks across Pinterest's microservices. Key challenges included ensuring data quality, scaling the infrastructure, and user education on tracing.