Mountpoint for Amazon S3 is a FUSE-based filesystem client that mounts S3 buckets as local directories, enabling standard file operations on objects without custom code. It enforces S3 bucket permissions through AWS Identity and Access Management policies on every operation, and implements lazy object materialization to fetch content on-demand rather than downloading entire objects at mount time. The filesystem maps S3's flat key namespace into a hierarchical directory structure using forward slashes as path separators, and supports write-back object assembly that accumulates local writes into a temporary buffer before uploading the complete object on file close.
The client distinguishes itself through parallel part-level throughput for read and write performance, a metadata caching layer that reduces S3 List and HeadObject calls with configurable time-to-live, and support for mounting via access point ARNs, bucket prefixes, Multi-Region Access Points, and Object Lambda Access Points. It provides mount-time controls for file permissions, ownership, and multi-user access, along with flags to restrict or allow file creation, deletion, overwriting, renaming, and appending. Storage class configuration for new objects, server-side encryption settings, and custom endpoint routing for IPv6, Transfer Acceleration, or PrivateLink are also available.
Additional capabilities include automatic boot-time mounting through fstab, FUSE file descriptor mounting for containerized environments, and network throughput and concurrency tuning for high-throughput workloads. The client exports internal FUSE and S3 request metrics via OpenTelemetry for monitoring, and supports local and shared object content caching to reduce redundant reads from the mounted bucket.
