Factor Exposure API (FastAPI Backend)

Quantitative Analytics & Risk Factor Engine for Indian Equities (Nifty 500)

The high-performance, asynchronous Python backend for the Factor Exposure Analyzer terminal. It utilizes advanced multivariate regression algorithms to calculate stock sensitivities ($\beta$ coefficients) against five critical risk factors and attributes variance-decomposition risk contributions.

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📈 Quantitative Factor Model

The engine downloads equity datasets dynamically via Yahoo Finance (yfinance) and estimates rolling Ordinary Least Squares (OLS) regressions against liquid proxies representing five market risk premiums:

$$R_i(t) - R_f = \alpha_i + \beta_{i,MKT}(R_{MKT}(t) - R_f) + \beta_{i,VAL}R_{VAL}(t) + \beta_{i,MOM}R_{MOM}(t) + \beta_{i,SZ}R_{SZ}(t) + \beta_{i,VOL}R_{VOL}(t) + \epsilon_i(t)$$

Factor Proxy	Underlying Metric	Yahoo Ticker
Nifty 50	Market Benchmark	^NSEI
Nifty Value 20	Value / Fundamental Cheapness	NV20BEES.NS
Nifty Momentum 50	Trend / Relative Strength	MOMOMENTUM.NS
Nifty Midcap 150	Size / Cap-weighted Premium	MID150BEES.NS
India VIX	Market Fear / Systemic Volatility	^INDIAVIX

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⚙️ Setup & Installation

Prerequisites

• Python: 3.10 or higher
• Dependencies: Listed in requirements.txt (statsmodels, scikit-learn, yfinance, pandas, supabase)

Local Setup

1. Navigate into the directory:

   cd factor-exposure-api

2. Initialize and activate virtual environment:

   # Windows
   python -m venv .venv
   .venv\Scripts\activate
   
   # macOS/Linux
   python3 -m venv .venv
   source .venv/bin/activate

3. Install requirements:

   pip install -r requirements.txt

4. Configure Environment Variables: Copy the example template to .env:

   cp .env.example .env

   Populate your custom rate limits, persistent Supabase keys, and server bindings.

5. Run server:

   python -m uvicorn main:app --host 127.0.0.1 --port 8000 --reload

   The OpenAPI/Swagger docs will be live at http://127.0.0.1:8000/docs.

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🚀 Deploying to Render (Best Practice)

This backend is ready for immediate deployment on Render (Free or Starter tier):

1. Create Render Web Service: Connect your GitHub repository to Render.
2. Configuration:
   • Environment: Python
   • Build Command: pip install -r requirements.txt
   • Start Command: uvicorn main:app --host 0.0.0.0 --port $PORT
3. Environment Variables:
   • PORT: 8000 (Render will override or map this automatically)
   • CORS_ORIGINS: Add your deployed Next.js URL (e.g., https://your-ui-subdomain.vercel.app)
   • LOG_LEVEL: INFO
   • SUPABASE_URL / SUPABASE_KEY (highly recommended to prevent API rate limiting from Yahoo Finance by utilizing shared cache storage).

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🔄 Heatmap Pre-Computation Pipeline

The system exposes a dedicated heatmap computation endpoint for portfolio-wide factor exposure analysis across the Nifty 500 universe:

Endpoint	Method	Description
/heatmap	GET	Returns computed factor betas for all tickers with sector aggregations
/heatmap/status	GET	Returns computation progress for a specific window (126D/252D/504D)
/heatmap/status/all	GET	Returns completion status for all windows in a single call

Pre-computation Workflow:

# Activate virtual environment
.venv\Scripts\activate

# Run the heatmap compute script (computes all 500 tickers)
python scripts/compute_heatmap.py

The script iterates through the Nifty 500 constituent list, performs rolling OLS regressions for each ticker against the five factor proxies, and stores results in Supabase. On a local machine, full computation takes approximately 45-60 minutes.

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💾 Supabase Caching Architecture

The API implements a TTL-based caching layer backed by Supabase to minimize repeated Yahoo Finance API calls:

Cache Table	Key	TTL	Purpose
factor_betas_cache	ticker + window_size	24 hours (configurable)	Individual stock factor regressions
heatmap_cache	ticker + window	Permanent	Pre-computed heatmap data

Graceful Degradation: If Supabase is unavailable (missing credentials or connectivity issues), the API falls back to on-demand computation. The service remains fully functional—albeit slower on cache misses.

Environment Variables:

SUPABASE_URL=https://your-project.supabase.co
SUPABASE_KEY=your-anon-key
CACHE_TTL_HOURS=24

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⚡ Rate Limiting & Performance

The API implements request throttling via slowapi:

• Default Limit: 10 requests/minute per IP
• Exempt Endpoints: /health, /heatmap/status, /heatmap/status/all
• Customization: Set via RATE_LIMIT environment variable (e.g., "50/minute")

For production deployments, we recommend:

1. Enabling Supabase caching to reduce Yahoo Finance API calls
2. Running weekly heatmap pre-computation via GitHub Actions
3. Using GitHub Actions cron job to ping /health every 10 minutes (see .github/workflows/keep_alive.yml)

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👥 Credits

Quantitative engine design, micro-service orchestration, and data fetching handlers by Sourabh.