Architecture¶

The Rust server is a Cargo workspace under crates/, split so the pure engines never depend on Python or WiredTiger:

Crate	What it is
`secantus-core`	The pure-Rust operator engines: query matcher, update engine, aggregation pipeline + expression evaluator, projection, sort keys, geo, collation. No PyO3, no WiredTiger — pure functions over BSON.
`secantus-storage`	The full WiredTiger-backed `Storage`: document/index/oplog tables, change-stream projection, transactions, backup/PITR archive + replay.
`secantus-wt`	The WiredTiger FFI bindings (bindgen over the vendored C library).
`secantus-server`	The server proper: wire protocol (`OP_MSG` / legacy handshake), command dispatch, cursors, auth (`secantus-auth`), TLS accept loop (rustls), CLI argument/config parsing.
`secantus-auth`	SCRAM-SHA-1/256 mechanics, X509 DN matching, RBAC role resolution.
`secantusdb`	The standalone binary crate — `secantusd-rs`. Its own workspace (it links WiredTiger); builds the vendored WT and statically links it.
`secantus-core-py`, `secantus-server-py`, `secantus-storage-py`	Thin PyO3 binding crates: `_secantus_core` (the parity-test vehicle), `_secantus_server` (the embedded `RustServer` handle), `_secantus_storage`. Python is only ever a launcher — never in the request path.

The WiredTiger-linked crates are excluded from the clean workspace so cargo fmt / clippy / test run fast and toolchain-light; the WT crates build inside the wheel (CMake + scikit-build-core) or the standalone binary build.

Parity with the Python server¶

Every Rust operator engine is pinned byte-for-byte to its pure-Python counterpart by parity test suites (curated corpora plus randomized fuzz). Where an exact reproduction isn’t achievable — Python-re regex semantics, some collation and Decimal128 edges — the Rust engine defers: it rejects the construct with a clean error rather than return a subtly different answer. That discipline is why the conformance numbers of the two servers track each other so closely.

Storage¶

Same model as the Python server, same on-disk schema: documents stored as opaque BSON blobs keyed by byte-sortable _id encodings, secondary indexes over typed sort-key columns, a natural-order (insertion) index, and the oplog/pre-image tables that back change streams and point-in-time recovery. A data directory written by one server opens in the other.

Versioning¶

All crates carry one lockstep version (0.MAJOR.PATCH-beta.N, SemVer pre-release) that advances independently of the PyPI package’s version. The canonical embedded value is secantus_server::VERSION, surfaced as buildInfo.secantusVersion over the wire, secantusd-rs --version on the CLI, and RustServer.version on the embedded handle. See Releases.