meridian-oss 1.1.7

Heroku for ML Features

Meridian

The Heroku for ML Features

Define features in Python. Get training data and production serving for free.

Stop paying the infrastructure tax. Meridian takes you from Jupyter to Production in 30 seconds.

📚 Read the Documentation | 🛠️ Unit Testing Guide

⚡ The 30-Second Quickstart

Option A: The "I just want to see it work" (Clone & Run)

git clone https://github.com/davidahmann/meridian.git
cd meridian
pip install -e ".[ui]"
meridian serve examples/basic_features.py

Option B: The "Builder" (Pip Install)

1. Install Meridian

pip install "meridian-oss[ui]"

2. Create a file named my_features.py:

from meridian.core import FeatureStore, entity, feature
from datetime import timedelta
import random

store = FeatureStore()

@entity(store)
class User:
    user_id: str

@feature(entity=User, refresh=timedelta(minutes=5), materialize=True)
def user_click_count(user_id: str) -> int:
    return len(user_id) + random.randint(0, 100)

3. Serve it immediately:

meridian serve my_features.py
# 🚀 Meridian server running on http://localhost:8000

4. Query it:

curl -X POST http://localhost:8000/features \
  -H "Content-Type: application/json" \
  -d '{"entity_name": "User", "entity_id": "u1", "features": ["user_click_count"]}'
# Output: {"user_click_count": 42}

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🚀 Why Meridian?

Most feature stores are built for the 1% of companies (Uber, DoorDash) with platform teams. They require Kubernetes, Spark, and complex microservices.

Meridian is built for the rest of us.

Feature	The "Old Way"	The Meridian Way
Config	500 lines of YAML	Python Decorators (@feature)
Infra	Kubernetes + Spark	Runs on your Laptop (DuckDB)
Serving	Complex API Gateway	meridian serve file.py
Philosophy	"Google Scale"	"Get it Shipped"

Key Features

• Local-First, Cloud-Ready: Runs on your laptop with zero dependencies (DuckDB + In-Memory). Scales to production with boring technology (Postgres + Redis).
• No Magic: Your code is your config. Explicit caching (materialize=True) and explicit refresh logic.
• Production Reliability: Built-in circuit breakers, fallback chains (Cache -> Compute -> Default), and Prometheus metrics (meridian_feature_requests_total).
• Self-Healing: Run meridian doctor to instantly diagnose config and connectivity issues.
• Rich UI & TUI: Includes a Streamlit dashboard with Visual Dependency Graphs and a production-grade Terminal UI for live monitoring.
• Hybrid Features (v1.1.0): Mix Python logic (for complex math) and SQL (for heavy joins) in the same API.
• Point-in-Time Correctness (v1.1.0): Zero data leakage using ASOF JOIN (DuckDB) and LATERAL JOIN (Postgres).
• Write Once, Run Anywhere (v1.1.0): Switch from Dev to Prod just by setting MERIDIAN_ENV=production. No code changes.

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🏗️ Architecture

Meridian is designed to grow with you.

graph TD
    subgraph Dev [Tier 1: Local Development]
        A[Laptop] -->|Uses| B(DuckDB)
        A -->|Uses| C(In-Memory Dict)
        style Dev fill:#e1f5fe,stroke:#01579b
    end

    subgraph Prod [Tier 2: Production]
        D[API Pods] -->|Async| E[(Postgres)]
        D -->|Async| F[(Redis)]
        style Prod fill:#fff3e0,stroke:#ff6f00
    end

    Switch{MERIDIAN_ENV} -->|development| Dev
    Switch -->|production| Prod

Tier 1: Local Development (The "Wedge")

• Perfect for prototyping and single-developer projects.
• Offline Store: DuckDB (Embedded)
• Online Store: Python Dictionary (In-Memory)
• Infra: None (Just pip install)

Tier 2: Production (The "Standard")

• Robust, scalable, and boring.
• Offline Store: Postgres / Snowflake / BigQuery
• Online Store: Redis
• Infra: 1x Postgres, 1x Redis, Nx API Pods

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🗺️ Roadmap

• ✅ Phase 1 (Now): Core API, DuckDB/Postgres support, Redis caching, FastAPI serving, PIT Correctness, Async I/O.
• 🚧 Phase 2: Drift detection, RBAC, and multi-region support.

🤝 Contributing

We love contributions! This is a community-driven project. Please read our CONTRIBUTING.md to get started.

📄 License

Apache 2.0