Choosing a backend

Storage is a LedgerBackend protocol, so the choice is one line and never leaks into your code. Start simple; upgrade when you need scale.

Backend	Use it for	One-liner
In-memory	Tests, demos, throwaway exploration	Ledger()
SQLite	Local persistence, single user, zero infra	Ledger.from_sqlite("inv.db")
JSON files	Git-friendly, human-readable, diff-able inventory	Ledger(JsonFileLedgerBackend("./inv"))
Snowflake	Production, org-scale, shared truth	Ledger.from_snowflake(conn, schema="DB.MODEL_LEDGER")
HTTP	Talk to a remote model-ledger REST service	Ledger(HttpLedgerBackend(url))

from model_ledger import Ledger
from model_ledger.backends.json_files import JsonFileLedgerBackend
from model_ledger.backends.http import HttpLedgerBackend

Ledger()                                                  # in-memory
Ledger.from_sqlite("./inventory.db")                      # SQLite
Ledger(JsonFileLedgerBackend("./inventory"))              # JSON files
Ledger.from_snowflake(conn, schema="DB.MODEL_LEDGER")     # Snowflake
Ledger(HttpLedgerBackend("https://model-ledger:8000"))    # remote REST

JSON files are git-friendly

The default JSON layout is meant to be inspected, diffed, and version-controlled — your inventory as plain text:

inventory/
├── models/
│   ├── fraud_scoring.json
│   └── churn_predictor.json
├── snapshots/
│   ├── a1b2c3d4.json
│   └── e5f6g7h8.json
└── tags/
    └── {model_hash}/production.json

Serving and the CLI

The CLI launches either agent or HTTP surfaces over any backend:

model-ledger serve --backend sqlite --path ./inventory.db --port 8000
model-ledger mcp   --backend snowflake --schema DB.MODEL_LEDGER

Snowflake reads credentials from the environment (SNOWFLAKE_ACCOUNT, SNOWFLAKE_USER, and either SNOWFLAKE_PASSWORD or SNOWFLAKE_AUTHENTICATOR=externalbrowser for SSO). Install the extra first: pip install "model-ledger[snowflake]".

Bring your own

Anything that satisfies the LedgerBackend protocol works — Postgres, DynamoDB, a graph DB. Implement the protocol methods and pass an instance to Ledger(...). See the API reference for the protocol surface.