Attic is a self-hostable Nix binary cache server written in Rust. It provides a multi-tenant, globally deduplicated cache for Nix store paths, supporting both local filesystem and S3-compatible storage backends. The system consists of a server binary (`atticd`) that implements the Nix binary cache HTTP API and a client CLI (`attic`) for authentication, pushing store paths, and managing caches. Authentication is stateless via signed JWTs (RS256/HS256) with fine-grained permissions per cache. The server uses content-defined chunking (FastCDC) to split NAR archives into variable-sized chunks, enabling deduplication at both the NAR and chunk levels. Compression (brotli, zstd, xz) is applied during upload with simultaneous hash computation for integrity verification. Garbage collection supports per-cache retention periods and cascading deletion from local caches to global chunk storage. The codebase is organized as a Cargo workspace with four crates: `attic` (core library with chunking, hashing, Nix store FFI), `server` (HTTP server, database, storage, garbage collection), `client` (CLI with push, watch-store, cache management), and `token` (JWT creation and verification). The architecture is modular, with clear separation between API handlers, database entities, storage backends, and authentication. While the project is still in early prototype stage with many TODOs and some fragile FFI bindings to Nix's C++ store library, it demonstrates solid engineering practices with reusable components like streaming hash readers, compression streams, and a custom serde serializer for Nix manifest format.