Architecture

 Python app ──► srvdb (Python package)
                  │  srvdb._low_level  (PyO3 bindings: argument conversion,
                  │                     error mapping, GIL release)
                  ▼
               srvdb (Rust core crate)
                  ├─ engine/    open, write, read, delete, commit, compact, modes
                  ├─ storage/   vector files, header, metadata (redb), index files, lock
                  ├─ index/     HNSW graph, IVF partitions, hybrid search
                  ├─ quant/     SQ8 and PQ quantization
                  ├─ distance/  SIMD cosine kernels and scans
                  └─ tuning/    auto mode

Principles:

• The core knows nothing about Python. Bindings stay thin; validation lives in the core so Rust users get it too.
• Committed data first. redb holds the commit record; vector files are append-only and truncated to the commit on open.
• Indexes are derived data, always rebuildable from the vectors.
• No network, no stdout. Logging goes through the log crate.

Engineering rules: AGENTS.md.