WarpStream is a Kafka protocol-compatible data streaming system built on top of object storage, designed to be cost-effective and efficient. It achieves this by minimizing object storage API calls while maintaining low latency and avoiding the need for local disks or inter-zone bandwidth costs. WarpStream's unique storage engine effectively decouples the relationship between the number of partitions in a workload and the number of object storage API requests made, scaling linearly with throughput at a rate more than 10x cheaper than paying for inter-zone bandwidth. The system uses a consistent hashing ring to distribute data across Agents, each of which caches a subset of files in memory using an in-memory cache that "mmaps" regions of files into memory. This approach eliminates the need for expensive GET requests and reduces waste by serving reads directly from object storage. Additionally, WarpStream compacting feature reduces read amplification and improves compression for some workloads.