SecantusDB 0.6.0b3

An embeddable, MongoDB compatible, document database, built on WiredTiger

[!WARNING] Beta software.

SecantusDB is past initial proving but the Python API surface (CLI flags, public class signatures) may still shift before 1.0. The on-disk format is WiredTiger's — the same engine MongoDB uses — and the schema we layer on top (collection / index / oplog tables) has been stable across releases; the test suite runs against real on-disk WiredTiger storage and the persistence tests explicitly verify close-and-reopen round-trips. That said, we don't yet ship a migration tool or a formal compatibility guarantee, so please don't put production data here yet — production deployments that need durable data across upgrades should still run a real mongod.

Drop-in MongoDB for single-node applications. SecantusDB is a real MongoDB server written in Python: it speaks the MongoDB wire protocol on the same TCP socket a mongod would, so any standard MongoDB driver or tool — pymongo, mongo-go-driver, mongosh, mongodump / mongorestore — connects unchanged. Point a MongoClient at it and your application code doesn't know the difference, as long as the application only needs single-node behaviour. No mongod to install, no port conflicts, parallel-test friendly, embedded or as a standalone daemon (secantusd-py).

Single-node only by design: replica sets, sharding, and anything that depends on real cluster topology are out of scope. Within that single-node scope, SecantusDB is the database your driver thinks it's talking to — same handshake, same wire frames, same error codes.

from pymongo import MongoClient
from secantus import SecantusDBServer

# On-disk by default at ./secantus-data; pass storage_path=":memory:" for ephemeral.
with SecantusDBServer(port=27017) as server:
    client = MongoClient(server.uri)
    db = client["mydb"]
    db["users"].insert_one({"_id": 1, "name": "Joe"})
    assert db["users"].find_one({"_id": 1})["name"] == "Joe"

Storage engine

SecantusDB uses the same WiredTiger C library mongod ships — vendored at vendor/wiredtiger/ (mongodb-7.0.33), built from source into the wheel, called via WT's official Python SWIG bindings. There is no Python re-implementation of the storage engine: B-trees, page eviction, write-ahead logging, durability, on-disk format are all pure WiredTiger. Your data lives on the same battle-tested engine mongod uses.

That doesn't make SecantusDB as fast as mongod — the layers above storage (command dispatch, query planner, aggregation pipeline) are Python, and a like-for-like benchmark currently has SecantusDB ~4×–17× slower per operation than mongod. CRUD reads sit near the lower end of that; bulk update / delete and aggregation sit at the upper end where Python loop overhead dominates. See docs/benchmark.md for current numbers and methodology. The right use is tests, dev, embedded apps, and single-node prototypes where conformance + WT durability matter more than per-op latency.

What's in scope

Everything a single-node application needs from the wire — the handshake (hello / isMaster / ping / buildInfo / ...), CRUD (insert / find / update / delete / findAndModify / count / drop), cursors with getMore / killCursors, aggregation pipelines and the expression language they need, and change streams (single-node, oplog-backed; collection / db / cluster scope; resume tokens; fullDocument: "updateLookup"; pre-images via fullDocumentBeforeChange; blocking awaitData getMore). All backed by a real query planner with index acceleration — single-field, compound, mixed-direction, partial, TTL, sort — proper explain output (IXSCAN vs COLLSCAN), and a hash-join $lookup.

Authentication: SCRAM-SHA-256 — MongoDB's default since 4.0 — is implemented end-to-end on the wire, alongside native TLS / mTLS and the MONGODB-X509 cert-as-username mechanism. Off by default; flip SCRAM on with secantusd-py --auth (or SecantusDBServer(..., require_auth=True)), provision users with createUser, then connect with the standard MongoClient(uri, username=, password=) shape. See Authentication. Authorization (RBAC) is not enforced — an authenticated principal is currently treated as fully privileged — and LDAP / Kerberos / GSSAPI / AWS / OIDC auth mechanisms are out of scope.

What's out of scope: real replica sets, sharding, RBAC, auth mechanisms beyond SCRAM-SHA-256 / MONGODB-X509 (no LDAP / Kerberos / GSSAPI / AWS / OIDC), OP_COMPRESSED, text / hashed / wildcard indexes, and $where / $function / $accumulator / mapReduce (no embedded JS runtime). If you need those, run a real mongod. Native TLS + mTLS, multi-document transactions (with WiredTiger-native rollback), and geo support ($geoWithin / $geoIntersects / $near / $nearSphere, $geoNear, 2dsphere and 2d indexes) are all in scope and shipped.

SQL / PostgreSQL interface (opt-in)

SecantusDB can also speak SQL over the PostgreSQL wire protocol. Install the extra (pip install "secantus[sql]"), start a SecantusPGServer — optionally sharing the same storage as the MongoDB server — and connect with psql, pg8000, or SQLAlchemy over a postgresql:// URL:

from secantus.sql import SecantusPGServer

with SecantusPGServer(port=5432) as server:
    ...  # SELECT / INSERT / UPDATE / DELETE, JOIN, GROUP BY, transactions, ...

Or run it as a standalone daemon — pip install "secantus[sql]" puts a secantusd-py-pg script on your PATH:

secantusd-py-pg --host 127.0.0.1 --port 5432 --storage-path ./secantus-data

SQL is compiled down to the same query / aggregation engines the MongoDB side uses, so it inherits index acceleration and the type system. A collection written with pymongo is queryable as a SQL table with no CREATE TABLE (schema-on-read), nested documents surface as jsonb (->, ->>, #>), and BEGIN / COMMIT / ROLLBACK are real transactions. Auth (SCRAM-SHA-256) and TLS work the same as on the Mongo side. See SQL / PostgreSQL interface for the supported-SQL matrix and examples.

Installation

pip install SecantusDB

Pre-built wheels are published for CPython 3.10, 3.11, 3.12, and 3.13 on:

• macOS arm64 (Apple Silicon)
• Linux x86_64 and aarch64 (manylinux2014 / glibc, and musllinux_1_2 / Alpine)
• Windows AMD64

macOS Intel (x86_64) is not in the wheel matrix; use a from-source install if you need it.

WiredTiger is vendored inside the wheel — no separate package, no compile step, no system build tools required.

Building from source (unsupported platforms only)

If your platform isn't in the matrix above, pip install SecantusDB falls back to the sdist and compiles WiredTiger from source. That needs three native build tools on PATH:

• cmake (>= 3.21)
• ninja
• swig (>= 4.0)

Platform	Install prerequisites
macOS (Homebrew)	brew install cmake ninja swig
Debian/Ubuntu	sudo apt-get install -y cmake ninja-build swig
Fedora/RHEL	sudo dnf install -y cmake ninja-build swig
Alpine	apk add --no-cache cmake ninja swig build-base

See Installation for dev-install instructions.

The Rust server (separate)

SecantusDB ships two separate servers on independent version lines: the pure-Python server (this package's SecantusDBServer) and a self-contained Rust server that speaks the same wire protocol off the GIL. You run one or the other — there is no in-process engine switching. The Python server is always pure-Python; the Rust engines live only in the Rust server.

The old in-process accelerator (SECANTUS_ENGINE=rust / SecantusDBServer(engine=...)) has been retired in favour of this two-server split.

The Rust side is a Cargo workspace under crates/: a pure-Rust engine crate (secantus-core, no PyO3) reused by the Rust server and the standalone secantusd-rs binary, plus a thin PyO3 bindings crate (secantus-core-py) that builds the secantus-core wheel — the vehicle that pins each Rust engine byte-for-byte against its pure-Python counterpart.

pip install "secantus[rust]"      # pulls the matching secantus-core wheel

The Python server is the conformance leader and the default choice: it passes 99.2% of pymongo's own test suite. The Rust server runs the same unmodified suite and currently passes 92.0% — it's faster per operation (see docs/benchmark.md) but is still closing the gap. The features the Rust server doesn't support yet — showExpandedEvents DDL change events, large change-event splitting, read / write-concern semantics, timeseries _id non-uniqueness — and a side-by-side of when to pick each server are spelled out in The two servers.

Standalone daemon (drop-in mongod replacement)

pip install puts a secantusd-py script on your PATH. Run it like you'd run mongod:

secantusd-py --host 127.0.0.1 --port 27017
# storage at ./secantus-data by default; pass --storage-path :memory:
# for an ephemeral temp dir cleaned up on shutdown.

The same pip install secantus also puts the standalone Rust server on your PATH as secantusd-rs (same flags, same wire protocol; see The two servers) — on Linux, macOS (Apple Silicon), and Windows. Intel-Mac wheels are pure-Python.

Then point any MongoDB driver or tool at it — no application code changes, just the URI:

mongosh mongodb://127.0.0.1:27017
mongodump --uri mongodb://127.0.0.1:27017 --out ./dump

from pymongo import MongoClient
client = MongoClient("mongodb://127.0.0.1:27017")  # same code as for mongod

The conformance gauges back this up: the official driver test suites run unmodified against SecantusDB — see the conformance validation summary.

Examples

A walk through the operations a typical application exercises — connect, insert, index, query, drop. Full version with explanations: examples in the docs.

from pymongo import MongoClient
from secantus import SecantusDBServer

# Ephemeral here so the snippet is self-contained; the production default
# is on-disk at ./secantus-data — drop storage_path or set a real path.
with SecantusDBServer(port=0, storage_path=":memory:") as server:
    client = MongoClient(server.uri)
    cellar = client["wine_cellar"]
    bottles = cellar["bottles"]

    # --- Insert ---
    bottles.insert_one(
        {"_id": 1, "name": "Pommard 2018", "region": "Burgundy", "year": 2018}
    )
    bottles.insert_many(
        [
            {"_id": 2, "name": "Brunello 2015", "region": "Tuscany", "year": 2015},
            {"_id": 3, "name": "Barolo 2017", "region": "Piedmont", "year": 2017},
            {"_id": 4, "name": "Pommard 2020", "region": "Burgundy", "year": 2020},
        ]
    )

    # --- Indexes ---
    bottles.create_index([("year", 1)])                     # single-field
    bottles.create_index([("region", 1), ("year", -1)])     # compound

    # --- Query ---
    drinkable_now = list(
        bottles.find({"year": {"$lte": 2018}}).sort("year")
    )
    assert [b["name"] for b in drinkable_now] == [
        "Brunello 2015",
        "Barolo 2017",
        "Pommard 2018",
    ]

    by_region = list(
        bottles.aggregate(
            [
                {"$group": {"_id": "$region", "count": {"$sum": 1}}},
                {"$sort": {"_id": 1}},
            ]
        )
    )

    # --- Drop ---
    bottles.drop()                              # one collection
    client.drop_database("wine_cellar")         # whole database

Documentation

Full docs are at secantusdb.com/docs — with the Rust server's own tree at secantusdb.com/docs/rust. Highlights:

• Quickstart — embedding in tests, running standalone.
• The two servers — Python vs Rust server, which to use, and what each doesn't support yet.
• Architecture — the layered design.
• Indexes — what find() and aggregate accelerate, explain semantics, hints, partial indexes, TTL.
• Aggregation — supported pipeline stages and expression operators.
• Compatibility — the divergences you should know about before you point an application at SecantusDB.
• Conformance validation — every supported driver's own test suite (pymongo, Go, Node, Java, Ruby, Rust, and the PHP library + extension) run unmodified against SecantusDB, with a cross-driver summary table and a per-driver report for each. The other-language gauges catch wire-protocol bugs that pymongo's permissive client accepts silently (e.g. int32-vs-int64 cursor ids).

Development

git clone https://github.com/jdrumgoole/SecantusDB.git
cd SecantusDB
uv sync --extra dev
uv run python -m pytest    # 584 tests, runs in parallel under pytest-xdist

Common workflows:

uv run python -m invoke fmt    # ruff format
uv run python -m invoke lint   # ruff check
uv run python -m invoke test   # pytest, parallel
uv run python -m invoke docs   # build Sphinx docs (warnings as errors)

License

SecantusDB is dual-licensed:

• Code — GPL-2.0-only. See LICENSE. SecantusDB bundles the WiredTiger storage engine (itself GPL-2/GPL-3), so the combined work is GPL.
• Written content — Creative Commons Attribution 4.0 International (CC-BY 4.0). See LICENSE-DOCS. Covers README.md, everything under docs/, the validation reports, and pymongo_validation/README.md. Operational instructions to AI assistants (CLAUDE.md) and vendored third-party content (under vendor/) are out of scope.