C0: A High-Performance Read-Through Cache for Object Storage

C0 is a high-performance HTTP API designed for caching immutable blobs in object storage. It leverages a hybrid memory and disk cache (powered by foyer) and works with any S3-compatible backend, but uses its own /fetch API requiring a precise Range header. Employing a fixed page size of 16 MiB, C0 maps requested byte ranges to page-aligned lookups, coalesces concurrent requests for the same page, and uses hedged requests to manage object storage tail latency. It can even attempt redundant buckets. C0 offers extensive configuration options, including timeout settings, retry mechanisms, and bucket prioritization, and provides performance monitoring via /stats and /metrics endpoints. Docker images are available.