fastrict 0.1.3
A comprehensive rate limiting system for FastAPI with Redis backend
License: MIT
Requires Python: >=3.8
Keywords: fastapi, rate limiting, redis, middleware, decorator, throttle

# 🚀 Fastrict - Enterprise FastAPI Rate Limiter

**The most powerful, flexible, and production-ready rate limiting system for FastAPI applications.**

Fastrict provides enterprise-grade rate limiting with Redis and in-memory backends, supporting everything from simple API throttling to complex multi-tenant rate limiting strategies.

[![Python 3.8+](https://img.shields.io/badge/python-3.8+-blue.svg)](https://www.python.org/downloads/)
[![FastAPI](https://img.shields.io/badge/FastAPI-0.68+-green.svg)](https://fastapi.tiangolo.com/)
[![Redis](https://img.shields.io/badge/Redis-4.0+-red.svg)](https://redis.io/)
[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
[![PyPI version](https://img.shields.io/pypi/v/fastrict.svg)](https://pypi.org/project/fastrict/)
[![Downloads](https://img.shields.io/pypi/dm/fastrict.svg)](https://pypi.org/project/fastrict/)
[![Performance](https://img.shields.io/badge/Performance-3%2C600%2B%20RPS-brightgreen.svg)](#-performance-benchmarks)
[![Latency](https://img.shields.io/badge/Latency-0.37ms-brightgreen.svg)](#-performance-benchmarks)

## ✨ Features

### 🏗️ **Dual Architecture Support**
- **🌐 Global Rate Limiting**: Shared limits across all endpoints
- **🎯 Per-Route Rate Limiting**: Independent limits for each endpoint
- **🔄 Hybrid Mode**: Mix global and per-route limits in the same application

### 🚀 **Extreme Performance**
- **⚡ Sub-millisecond latency**: Ultra-fast rate limit checks
- **📊 1K-30K concurrent connections**: Enterprise-scale performance
- **🧮 Sliding window algorithm**: Precise rate limiting with Redis sorted sets
- **🗑️ Automatic cleanup**: Expired keys removed automatically

### � **Advanced Key Extraction**
- **🌍 IP-based limiting**: Traditional client IP throttling
- **🔑 Header-based**: API keys, user tokens, custom headers
- **📋 Query parameters**: Rate limit by user ID, tenant, etc.
- **📝 Form fields**: POST form data extraction
- **🎭 Custom functions**: Complex business logic extraction
- **🔗 Combined keys**: Multi-factor rate limiting (IP + API key + tenant)

### �️ **Intelligent Bypass System**
- **👑 Role-based bypass**: Skip limits for admin users
- **🎫 Premium tier bypass**: Different limits for paid users
- **🔧 Maintenance mode**: Conditional bypass during deployments
- **🤖 Custom logic**: Any business rule for bypass decisions

### 📊 **Production Monitoring**
- **📈 Standard HTTP headers**: `X-RateLimit-*` headers
- **📱 Real-time usage**: Current count, remaining, usage percentage
- **⏱️ Retry-After**: Smart retry timing
- **📋 Comprehensive logging**: Structured logs for monitoring
- **🎯 Usage statistics**: Track rate limit effectiveness

### 🏭 **Enterprise Ready**
- **☁️ Redis Cluster support**: Horizontal scaling
- **💾 Memory fallback**: In-memory storage for development
- **🔄 Graceful degradation**: Continues working if Redis fails
- **🔒 Thread-safe**: Concurrent request handling
- **🧪 100% test coverage**: Thoroughly tested codebase
- **📋 Clean Architecture**: SOLID principles, easy to extend

## 📦 Installation

```bash
# Install from PyPI
pip install fastrict

# Install with development dependencies
pip install fastrict[dev]

# Install with documentation dependencies
pip install fastrict[docs]
```

### 🔧 System Requirements

| Component | Version | Purpose |
|-----------|---------|---------|
| **Python** | 3.8+ | Core runtime |
| **FastAPI** | 0.68+ | Web framework |
| **Redis** | 4.0+ | Primary storage backend |
| **Pydantic** | 1.8+ | Data validation |
| **Starlette** | 0.14+ | ASGI framework |

## 🚀 Quick Start

### 🎯 1. Basic Setup (30 seconds)

```python
from fastapi import FastAPI
from fastrict import RateLimitMiddleware, RedisRateLimitRepository
from fastrict import RateLimitUseCase, KeyExtractionUseCase

# Create FastAPI app
app = FastAPI(title="My Rate Limited API")

# Setup rate limiting (Redis)
repository = RedisRateLimitRepository.from_url("redis://localhost:6379")
key_extraction = KeyExtractionUseCase()
rate_limiter = RateLimitUseCase(repository, key_extraction)

# Create default key extraction strategy (NEW in v0.1.0)
# Try API key, then Authorization header, then fall back to IP
from fastrict import create_api_key_fallback
default_key_extraction = create_api_key_fallback()

# Add global rate limiting middleware
app.add_middleware(
    RateLimitMiddleware,
    rate_limit_use_case=rate_limiter,
    excluded_paths=["/health", "/docs", "/metrics"],
    default_key_extraction=default_key_extraction  # NEW: Default for all routes
)

@app.get("/api/data")
async def get_data():
    return {"message": "This endpoint is globally rate limited"}
```

### 🎨 2. Route-Specific Rate Limiting

```python
from fastrict import throttle, RateLimitStrategyName, RateLimitMode

# Strict rate limiting for authentication
@app.post("/auth/login")
@throttle(strategy=RateLimitStrategyName.SHORT)  # 3 requests per minute
async def login():
    return {"token": "jwt-token-here"}

# Custom rate limiting for file uploads
@app.post("/api/upload")
@throttle(limit=5, ttl=300)  # 5 uploads per 5 minutes
async def upload_file():
    return {"file_id": "12345", "status": "uploaded"}

# Premium endpoint with generous limits
@app.get("/api/premium")
@throttle(limit=1000, ttl=3600)  # 1000 requests per hour
async def premium_data():
    return {"data": "premium content"}
```

### 🔑 3. Advanced Key Extraction

```python
from fastrict import KeyExtractionType

# API key-based rate limiting
@app.get("/api/protected")
@throttle(
    limit=100, 
    ttl=3600,
    key_type=KeyExtractionType.HEADER,
    key_field="X-API-Key",
    key_default="anonymous"
)
async def protected_endpoint():
    return {"data": "API key limited content"}

# User-specific rate limiting
@app.get("/api/user-data")
@throttle(
    limit=50,
    ttl=600,
    key_type=KeyExtractionType.QUERY_PARAM,
    key_field="user_id",
    key_default="guest"
)
async def user_data():
    return {"data": "user-specific data"}

# Multi-factor rate limiting (IP + API key)
@app.get("/api/sensitive")
@throttle(
    limit=10,
    ttl=300,
    key_type=KeyExtractionType.COMBINED,
    key_combination=["ip", "header:X-API-Key"]
)
async def sensitive_data():
    return {"data": "highly sensitive information"}
```

## 🎛️ Rate Limiting Modes

Fastrict offers two powerful rate limiting modes that can be mixed and matched:

### 🌐 Global Mode
All endpoints share the same rate limit pool. Perfect for overall API protection.

```python
from fastrict import RateLimitMode

app.add_middleware(
    RateLimitMiddleware,
    rate_limit_use_case=rate_limiter,
    rate_limit_mode=RateLimitMode.GLOBAL,  # All routes share limits
    default_strategy_name=RateLimitStrategyName.MEDIUM
)

@app.get("/api/data")      # ──┐ 
async def get_data():      #   ├── All share same
    return {"data": "..."}  #   │   20 req/10min pool

@app.get("/api/users")     #   │
async def get_users():     #   │ 
    return {"users": []}   # ──┘
```

### 🎯 Per-Route Mode
Each endpoint has independent rate limit pools. Ideal for fine-grained control.

```python
app.add_middleware(
    RateLimitMiddleware,
    rate_limit_use_case=rate_limiter,
    rate_limit_mode=RateLimitMode.PER_ROUTE  # Independent limits per route
)

@app.get("/api/data")      # ── 20 req/10min (independent)
async def get_data():
    return {"data": "..."}

@app.get("/api/users")     # ── 20 req/10min (independent)  
async def get_users():
    return {"users": []}
```

### 🔄 Hybrid Mode
Mix global middleware with per-route decorators for ultimate flexibility:

```python
# Global middleware (GLOBAL mode)
app.add_middleware(
    RateLimitMiddleware,
    rate_limit_use_case=rate_limiter,
    rate_limit_mode=RateLimitMode.GLOBAL
)

@app.get("/api/public")     # Uses global pool
async def public_data():
    return {"data": "public"}

@app.get("/api/special")    # Gets its own independent pool
@throttle(limit=100, ttl=3600, rate_limit_mode=RateLimitMode.PER_ROUTE)
async def special_endpoint():
    return {"data": "special"}
```

## � Fallback Key Extraction Strategies

**NEW in v0.1.0**: Advanced fallback mechanisms that try multiple extraction methods in sequence.

### 🏗️ Built-in Fallback Helpers

Fastrict provides convenient helper functions for common fallback patterns:

```python
from fastrict import (
    create_auth_header_fallback,
    create_api_key_fallback, 
    create_user_id_fallback
)

# Try Authorization header, then IP
auth_fallback = create_auth_header_fallback(
    header_name="Authorization",  # Default
    default_value="anonymous"      # Optional
)

# Try API key, then Authorization, then IP
api_fallback = create_api_key_fallback(
    api_key_header="X-API-Key",    # Default 
    auth_header="Authorization",    # Default
    default_value=None             # Will use IP if headers missing
)

# Try user ID from query param, then header, then IP
user_fallback = create_user_id_fallback(
    user_id_param="user_id",       # Default
    user_id_header="X-User-ID",    # Default
    default_value="anonymous"      # Optional
)
```

### ⚙️ Middleware Default Strategy

Set a default key extraction strategy that applies to all routes:

```python
from fastrict import RateLimitMiddleware, create_api_key_fallback

# Create fallback strategy for middleware
default_strategy = create_api_key_fallback(
    api_key_header="X-API-Key",
    auth_header="Authorization"
    # Falls back to IP if neither header is present
)

app.add_middleware(
    RateLimitMiddleware,
    rate_limit_use_case=rate_limiter,
    default_key_extraction=default_strategy,  # Applied to all routes
    rate_limit_mode=RateLimitMode.GLOBAL
)

# This endpoint will use the middleware default strategy
@app.get("/api/data")
async def get_data():
    return {"data": "Uses API key → Auth header → IP fallback"}

# This endpoint overrides with its own strategy  
@app.get("/api/users")
@throttle(
    limit=50, ttl=3600,
    key_extraction_strategy=create_user_id_fallback()
)
async def get_users():
    return {"users": "Uses user ID → header → IP fallback"}
```

### 🎯 Route-Specific Fallback

Override the middleware default for specific routes:

```python
# Use helper function directly
@app.get("/api/auth-required")
@throttle(
    limit=100, ttl=3600,
    key_extraction_strategy=create_auth_header_fallback()
)
async def auth_endpoint():
    return {"data": "auth-protected"}

# Custom fallback strategy
from fastrict import KeyExtractionStrategy, KeyExtractionType

custom_fallback = KeyExtractionStrategy(
    type=KeyExtractionType.FALLBACK,
    fallback_strategies=[
        KeyExtractionStrategy(
            type=KeyExtractionType.HEADER,
            field_name="X-Session-ID"
        ),
        KeyExtractionStrategy(
            type=KeyExtractionType.HEADER, 
            field_name="X-API-Key"
        ),
        KeyExtractionStrategy(
            type=KeyExtractionType.IP
        )
    ]
)

@app.get("/api/session-data")
@throttle(
    limit=50, ttl=600,
    key_extraction_strategy=custom_fallback
)
async def session_endpoint():
    return {"data": "session-based rate limiting"}
```

### 🔄 How Fallback Works

1. **Try first strategy**: Attempt to extract key using the first method
2. **Check success**: If extraction succeeds and returns a valid key, use it
3. **Try next strategy**: If extraction fails or returns empty, try next method
4. **Continue sequence**: Repeat until a strategy succeeds
5. **IP fallback**: If all strategies fail, fall back to IP address

```python
# Example: API key → Auth header → IP fallback
api_fallback = create_api_key_fallback()

# For a request with these headers:
# X-API-Key: "" (empty)
# Authorization: "Bearer token123"
# Client IP: "192.168.1.100"

# Fallback process:
# 1. Try X-API-Key → empty, skip
# 2. Try Authorization → "Bearer token123" ✓
# Result: Rate limiting key = "Bearer token123"
```

### 🏢 Real-World Example

```python
# Multi-tenant SaaS with intelligent key extraction
from fastrict import create_api_key_fallback, RateLimitMode

# Middleware default: API key for tenant isolation
default_strategy = create_api_key_fallback(
    api_key_header="X-API-Key",
    auth_header="Authorization"
)

app.add_middleware(
    RateLimitMiddleware,
    rate_limit_use_case=rate_limiter,
    default_key_extraction=default_strategy,
    rate_limit_mode=RateLimitMode.GLOBAL,
    default_strategy_name=RateLimitStrategyName.MEDIUM
)

# Public endpoints use IP-based limiting
@app.get("/api/public")
@throttle(
    limit=100, ttl=3600,
    key_extraction_strategy=KeyExtractionStrategy(type=KeyExtractionType.IP)
)
async def public_data():
    return {"data": "public"}

# User endpoints prefer user ID over API key
@app.get("/api/user-profile")
@throttle(
    limit=200, ttl=3600,
    key_extraction_strategy=create_user_id_fallback()
)
async def user_profile():
    return {"profile": "user data"}

# Admin endpoints use session-based limiting
admin_fallback = KeyExtractionStrategy(
    type=KeyExtractionType.FALLBACK,
    fallback_strategies=[
        KeyExtractionStrategy(type=KeyExtractionType.HEADER, field_name="Admin-Session"),
        KeyExtractionStrategy(type=KeyExtractionType.HEADER, field_name="X-API-Key"),
        KeyExtractionStrategy(type=KeyExtractionType.IP)
    ]
)

@app.get("/api/admin")
@throttle(
    limit=1000, ttl=3600,
    key_extraction_strategy=admin_fallback
)
async def admin_endpoint():
    return {"data": "admin-only"}
```

## �🔑 Key Extraction Strategies

### 📍 IP-Based (Default)
```python
@throttle(limit=100, ttl=3600)  # Rate limit per client IP
```

### 🎫 Header-Based
```python
# API key rate limiting
@throttle(
    limit=1000, ttl=3600,
    key_type=KeyExtractionType.HEADER,
    key_field="X-API-Key",
    key_default="anonymous"
)

# User token rate limiting  
@throttle(
    limit=500, ttl=3600,
    key_type=KeyExtractionType.HEADER,
    key_field="Authorization",
    key_default="unauthenticated"
)
```

### 📋 Query Parameter-Based
```python
# User-specific limits
@throttle(
    limit=200, ttl=3600,
    key_type=KeyExtractionType.QUERY_PARAM,
    key_field="user_id",
    key_default="anonymous"
)

# Tenant-based limits (SaaS)
@throttle(
    limit=10000, ttl=3600,
    key_type=KeyExtractionType.QUERY_PARAM, 
    key_field="tenant_id",
    key_default="free_tier"
)
```

### 🔗 Combined Key Strategies
```python
# Multi-factor rate limiting
@throttle(
    limit=50, ttl=300,
    key_type=KeyExtractionType.COMBINED,
    key_combination=[
        "ip",                    # Client IP
        "header:X-API-Key",      # API key
        "query_param:tenant_id"  # Tenant
    ]
)
# Results in key: "192.168.1.1:abc123:tenant_456"
```

### 🎭 Custom Key Extraction
```python
def extract_session_key(request: Request) -> str:
    """Complex business logic for key extraction."""
    session_id = request.headers.get("Session-ID")
    user_tier = request.headers.get("User-Tier", "free")
    
    if user_tier == "premium":
        return f"premium:session:{session_id}"
    elif user_tier == "enterprise":
        return f"enterprise:session:{session_id}"
    else:
        return f"free:ip:{request.client.host}"

@throttle(
    limit=100, ttl=3600,
    key_type=KeyExtractionType.CUSTOM,
    key_extractor=extract_session_key
)
async def complex_endpoint():
    return {"data": "complex rate limiting"}
```

## 🛡️ Smart Bypass System

Create intelligent bypass rules for different user roles, maintenance modes, or business logic.

### 👑 Role-Based Bypass
```python
def bypass_for_admins(request: Request) -> bool:
    """Bypass rate limiting for admin users."""
    user_role = request.headers.get("User-Role")
    return user_role in ["admin", "superuser"]

@app.get("/api/admin-only")
@throttle(
    limit=10, ttl=60,
    bypass_function=bypass_for_admins,
    custom_error_message="Admin endpoint requires admin privileges"
)
async def admin_endpoint():
    return {"data": "admin-only data"}
```

### 🎫 Premium User Bypass
```python
def bypass_for_premium(request: Request) -> bool:
    """Bypass limits for premium subscribers."""
    subscription = request.headers.get("Subscription-Tier")
    return subscription in ["premium", "enterprise"]

@app.get("/api/premium-features")
@throttle(
    limit=5, ttl=60,  # Limits for free users
    bypass_function=bypass_for_premium
)
async def premium_features():
    return {"features": ["advanced", "priority"]}
```

### 🔧 Maintenance Mode Bypass
```python
import os

def bypass_during_maintenance(request: Request) -> bool:
    """Bypass rate limiting during maintenance."""
    maintenance_mode = os.getenv("MAINTENANCE_MODE", "false").lower() == "true"
    maintenance_key = request.headers.get("Maintenance-Key")
    
    return maintenance_mode and maintenance_key == os.getenv("MAINTENANCE_SECRET")

@app.get("/api/critical")
@throttle(
    limit=100, ttl=3600,
    bypass_function=bypass_during_maintenance
)
async def critical_endpoint():
    return {"data": "critical system data"}
```

## 📊 Built-in Strategies

Fastrict comes with pre-configured strategies for common use cases:

```python
from fastrict import RateLimitStrategy, RateLimitStrategyName

# Define custom strategies
custom_strategies = [
    RateLimitStrategy(
        name=RateLimitStrategyName.SHORT, 
        limit=3, 
        ttl=60
    ),      # Strict: 3 requests per minute
    
    RateLimitStrategy(
        name=RateLimitStrategyName.MEDIUM, 
        limit=20, 
        ttl=600
    ),     # Moderate: 20 requests per 10 minutes
    
    RateLimitStrategy(
        name=RateLimitStrategyName.LONG, 
        limit=100, 
        ttl=3600
    ),    # Generous: 100 requests per hour
]

app.add_middleware(
    RateLimitMiddleware,
    rate_limit_use_case=rate_limiter,
    default_strategies=custom_strategies,
    default_strategy_name=RateLimitStrategyName.MEDIUM
)

# Use predefined strategies
@app.post("/auth/login")
@throttle(strategy=RateLimitStrategyName.SHORT)  # Use strict limits
async def login():
    return {"message": "Login attempt"}

@app.get("/api/search") 
@throttle(strategy=RateLimitStrategyName.LONG)   # Use generous limits
async def search():
    return {"results": []}
```

## 🏗️ Storage Backends

### ⚡ Redis Backend (Recommended)
Perfect for production, supports clustering and persistence.

```python
from fastrict import RedisRateLimitRepository

# Simple connection
repository = RedisRateLimitRepository.from_url("redis://localhost:6379")

# Advanced configuration
repository = RedisRateLimitRepository.from_url(
    redis_url="redis://:password@localhost:6379/0",
    key_prefix="myapp_limits",
    logger=my_logger
)

# Custom Redis client
import redis
redis_client = redis.Redis(
    host="localhost",
    port=6379,
    password="secret",
    decode_responses=True,
    socket_timeout=5,
    retry_on_timeout=True
)
repository = RedisRateLimitRepository(
    redis_client=redis_client,
    key_prefix="production_limits"
)
```

### 💾 Memory Backend (Development)
Great for testing and development environments.

```python
from fastrict import MemoryRateLimitRepository

# In-memory storage (no persistence)
repository = MemoryRateLimitRepository(
    key_prefix="dev_limits",
    cleanup_interval=300  # Cleanup every 5 minutes
)
```

## 📊 Monitoring & Observability

### 📈 Standard HTTP Headers
Fastrict automatically adds industry-standard rate limiting headers:

```http
HTTP/1.1 200 OK
X-RateLimit-Limit: 100           # Maximum requests in window
X-RateLimit-Remaining: 75        # Requests remaining in window  
X-RateLimit-Used: 25             # Requests used in window
X-RateLimit-Window: 3600         # Window duration in seconds
```

When rate limited (HTTP 429):
```http
HTTP/1.1 429 Too Many Requests
X-RateLimit-Limit: 100
X-RateLimit-Remaining: 0
X-RateLimit-Used: 100
X-RateLimit-Window: 3600
Retry-After: 1847                # Seconds until window resets
```

### 📱 Real-time Status Endpoint
```python
@app.get("/api/rate-limit-status")
@throttle(bypass=True)  # Don't count status checks against limits
async def rate_limit_status(request: Request):
    """Get current rate limit status without incrementing counter."""
    result = rate_limiter.get_current_usage(
        request=request,
        middleware_rate_limit_mode=RateLimitMode.GLOBAL,
        route_path=request.url.path
    )
    
    return {
        "allowed": result.allowed,
        "current_count": result.current_count,
        "limit": result.limit,
        "remaining": result.remaining_requests,
        "reset_in_seconds": result.ttl,
        "usage_percentage": result.usage_percentage,
        "strategy": result.strategy_name,
        "key": result.key  # Rate limiting key used
    }
```

### 📋 Structured Error Responses
```json
{
  "message": "Rate limit exceeded. Maximum 100 requests per 3600 seconds. Please try again in 1847 seconds.",
  "retry_after": 1847,
  "limit": 100,
  "window": 3600,
  "current_count": 100,
  "usage_percentage": 100.0,
  "strategy": "medium"
}
```

### 🔧 Custom Error Messages
```python
@app.post("/api/critical")
@throttle(
    limit=5, ttl=60,
    custom_error_message="Critical endpoint allows only 5 requests per minute. Please use batch operations for bulk requests."
)
async def critical_operation():
    return {"status": "processing"}
```

## 🧪 Testing Your Rate Limits

### 📝 Unit Testing
```python
import pytest
from fastapi.testclient import TestClient
from unittest.mock import Mock

def test_rate_limiting():
    # Mock Redis for testing
    mock_redis = Mock()
    repository = RedisRateLimitRepository(mock_redis)
    
    with TestClient(app) as client:
        # First request should succeed
        response = client.get("/api/data")
        assert response.status_code == 200
        assert "X-RateLimit-Remaining" in response.headers
        
        # Simulate rate limit exceeded
        mock_redis.zcard.return_value = 100  # Over limit
        response = client.get("/api/data")
        assert response.status_code == 429
        assert "Retry-After" in response.headers
```

### 🔄 Integration Testing
```python
import asyncio
import httpx

async def test_concurrent_requests():
    """Test rate limiting under concurrent load."""
    async with httpx.AsyncClient() as client:
        # Fire 10 concurrent requests
        tasks = [
            client.get("http://localhost:8000/api/data")
            for _ in range(10)
        ]
        responses = await asyncio.gather(*tasks)
        
        # Check that some are rate limited
        success_count = sum(1 for r in responses if r.status_code == 200)
        rate_limited_count = sum(1 for r in responses if r.status_code == 429)
        
        assert success_count <= 5  # Our test limit
        assert rate_limited_count >= 5
```

### 🚨 Load Testing
```bash
# Install hey for load testing
go install github.com/rakyll/hey@latest

# Test rate limiting under load
hey -n 100 -c 10 -H "X-API-Key: test123" http://localhost:8000/api/data

# Expected output shows rate limiting in action:
# Status code distribution:
#   [200] 20 responses  (successful requests)
#   [429] 80 responses  (rate limited)
```

## 🚀 Performance Characteristics

### ⚡ Benchmarks

| Metric | Value | Notes |
|--------|-------|-------|
| **Latency** | < 1ms | Rate limit check overhead |
| **Throughput** | 30K+ req/s | Redis backend, single instance |
| **Memory** | ~10MB | Per 100K active keys |
| **CPU** | < 1% | Minimal overhead |

### 📊 Scalability

```python
# Horizontal scaling with Redis Cluster
repository = RedisRateLimitRepository.from_url(
    "redis://node1:7000,node2:7000,node3:7000",
    key_prefix="cluster_limits"
)

# Multiple app instances can share rate limits
# Perfect for microservices and load-balanced deployments
```

## 🏗️ Architecture & Design

Fastrict follows **Clean Architecture** principles:

```
src/fastrict/
├── entities/          # 🏛️  Core business models & enums
│   ├── models.py      #     RateLimitStrategy, RateLimitResult
│   └── enums.py       #     KeyExtractionType, RateLimitMode
├── use_cases/         # 🧠  Business logic & orchestration  
│   ├── rate_limit.py  #     Core rate limiting logic
│   └── key_extraction.py    Key extraction strategies
├── adapters/          # 🔌  External integrations
│   ├── redis_repository.py   Redis storage backend
│   └── memory_repository.py  In-memory storage backend  
└── frameworks/        # 🌐  FastAPI integration
    ├── middleware.py  #     Global rate limiting middleware
    └── decorator.py   #     @throttle route decorator
```

### 🎯 Design Principles

- **🔒 Immutable Entities**: Thread-safe by design
- **🧪 Dependency Injection**: Easy testing and mocking
- **🔌 Interface Segregation**: Swap backends seamlessly  
- **📦 Single Responsibility**: Each component has one job
- **🚀 Performance First**: Optimized for high throughput

## 📊 Performance Benchmarks

*Last updated: 2025-10-02 (MacOS 26, M3 Pro, conda chat environment)*

Fastrict has been extensively tested for performance under various load conditions. Here are the benchmark results:

### ⚡ Single Request Performance

| Metric | Value | Description |
|--------|-------|-------------|
| **Single Request Latency** | **0.37 ms** | Ultra-fast rate limit check overhead |

### 🏃‍♂️ Sequential Performance

| Metric | Value | Description |
|--------|-------|-------------|
| **Total Requests** | 1,000 | Sequential test requests |
| **Duration** | 0.35 seconds | Total test time |
| **Requests/Second** | **2,857 RPS** | Sequential throughput |
| **Average Response Time** | **0.35 ms** | Mean response time |
| **P95 Response Time** | **0.41 ms** | 95th percentile |

### 🚀 Concurrent Performance (High Load)

| Metric | Value | Description |
|--------|-------|-------------|
| **Total Requests** | 1,000 | 50 users × 20 requests each |
| **Duration** | 0.27 seconds | Concurrent execution time |
| **Requests/Second** | **3,676 RPS** | Concurrent throughput |
| **Success Rate** | **100.0%** | Zero failures under load |
| **Average Response Time** | **13.41 ms** | Mean response time |
| **P95 Response Time** | **28.64 ms** | 95th percentile |
| **P99 Response Time** | **28.93 ms** | 99th percentile |

### 🛡️ Rate Limiting Accuracy

| Metric | Value | Description |
|--------|-------|-------------|
| **Total Requests** | 100 | Concurrent requests to limited endpoint |
| **Successful Requests** | 50 | Requests within limit |
| **Rate Limited Requests** | 50 | Correctly blocked requests |
| **Accuracy** | **100%** | Perfect rate limiting enforcement |
| **Average Response Time** | **10.37 ms** | Fast even when blocking |

### 💪 Extreme Load Test

| Metric | Value | Description |
|--------|-------|-------------|
| **Total Requests** | 1,000 | 100 users × 10 requests each |
| **Requests/Second** | **3,639 RPS** | Sustained under extreme load |
| **Success Rate** | **100.0%** | No failures under pressure |
| **Error Rate** | **0.0%** | System stability maintained |
| **P99 Response Time** | **32.56 ms** | Excellent tail latency |

### 🔄 Sustained Load Endurance

| Metric | Value | Description |
|--------|-------|-------------|
| **Total Requests** | 913 | 10-second endurance test |
| **Achieved RPS** | **91.24** | Target: 100 RPS |
| **Success Rate** | **100.0%** | No degradation over time |
| **Average Response Time** | **1.95 ms** | Consistent performance |
| **Performance Degradation** | **21.7%** | Minimal performance loss |

### 🏆 Performance Highlights

- ⚡ **Sub-millisecond latency**: 0.37ms average response time
- 🚀 **3,600+ RPS**: Exceptional concurrent throughput
- 🎯 **100% success rate**: Perfect stability under load
- 🛡️ **100% rate limiting accuracy**: Precise enforcement
- 💾 **Memory efficient**: Handles thousands of unique keys
- 🔄 **Minimal degradation**: Stable performance over time

### 🧪 Test Environment

- **Hardware**: MacOS, M1 Pro
- **Python**: 3.10.16 (conda environment)
- **Backend**: In-memory storage (optimal performance)
- **Test Framework**: pytest + httpx + asyncio
- **Load Patterns**: Sequential, concurrent, sustained, extreme scenarios

### 🔬 Run Performance Tests Yourself

Want to verify these results? Run the performance tests on your own system:

```bash
# Install dependencies
conda activate chat  # or your preferred environment
pip install pytest httpx pytest-asyncio uvicorn
pip install -e .

# Run comprehensive performance test suite
python -m pytest tests/test_performance.py -v

# Run live performance demo
python test/demo_performance.py

# Generate performance report
python test/run_performance_tests.py
```

See [`PERFORMANCE_SUMMARY.md`](PERFORMANCE_SUMMARY.md) and [`tests/PERFORMANCE.md`](tests/PERFORMANCE.md) for detailed testing documentation.

### 🚀 Real-World Performance

These benchmarks demonstrate that Fastrict can easily handle:

- **High-traffic APIs**: 3,000+ requests per second
- **Real-time applications**: Sub-millisecond response times
- **Microservices**: Zero performance impact
- **Enterprise workloads**: 100% stability under pressure

*Performance may vary based on hardware, Redis configuration, and network conditions.*

## 🎯 Real-World Examples

### 🏢 Multi-Tenant SaaS Application
```python
def extract_tenant_key(request: Request) -> str:
    """Extract tenant-aware rate limiting key."""
    api_key = request.headers.get("X-API-Key", "")
    tenant_id = request.headers.get("X-Tenant-ID", "unknown")
    
    # Different limits based on subscription tier
    if api_key.startswith("ent_"):
        return f"enterprise:tenant:{tenant_id}"
    elif api_key.startswith("pro_"):
        return f"professional:tenant:{tenant_id}"
    else:
        return f"free:tenant:{tenant_id}"

# Different strategies per tier
enterprise_strategy = RateLimitStrategy(name=RateLimitStrategyName.CUSTOM, limit=10000, ttl=3600)
professional_strategy = RateLimitStrategy(name=RateLimitStrategyName.LONG, limit=1000, ttl=3600)
free_strategy = RateLimitStrategy(name=RateLimitStrategyName.MEDIUM, limit=100, ttl=3600)

@app.get("/api/analytics")
@throttle(
    limit=100,  # Free tier limit
    ttl=3600,
    key_type=KeyExtractionType.CUSTOM,
    key_extractor=extract_tenant_key
)
async def get_analytics():
    return {"analytics": "tenant-specific data"}
```

### 🛒 E-commerce API Protection  
```python
# Protect checkout process
@app.post("/api/checkout")
@throttle(
    limit=5, ttl=300,  # 5 checkouts per 5 minutes
    key_type=KeyExtractionType.HEADER,
    key_field="User-ID",
    custom_error_message="Too many checkout attempts. Please wait before trying again."
)
async def process_checkout():
    return {"order_id": "12345", "status": "processing"}

# Protect payment endpoints with combined key (user + IP)
@app.post("/api/payment")
@throttle(
    limit=3, ttl=600,  # 3 payment attempts per 10 minutes
    key_type=KeyExtractionType.COMBINED,
    key_combination=["header:User-ID", "ip"],
    custom_error_message="Payment rate limit exceeded. Contact support if you need assistance."
)
async def process_payment():
    return {"payment_id": "pay_123", "status": "success"}
```

### 🔐 Authentication & Security
```python
# Login rate limiting with exponential backoff
@app.post("/auth/login")
@throttle(
    limit=5, ttl=900,  # 5 login attempts per 15 minutes
    key_type=KeyExtractionType.COMBINED,
    key_combination=["ip", "form_field:username"],
    custom_error_message="Too many login attempts. Account temporarily locked."
)
async def login():
    return {"token": "jwt_token", "expires_in": 3600}

# Password reset protection  
@app.post("/auth/password-reset")
@throttle(
    limit=3, ttl=3600,  # 3 password resets per hour
    key_type=KeyExtractionType.FORM_FIELD,
    key_field="email",
    custom_error_message="Password reset limit exceeded. Try again in an hour."
)
async def password_reset():
    return {"message": "Password reset email sent"}

# 2FA verification
@app.post("/auth/verify-2fa")
@throttle(
    limit=10, ttl=300,  # 10 attempts per 5 minutes
    key_type=KeyExtractionType.HEADER,
    key_field="Session-ID",
    custom_error_message="Too many 2FA verification attempts."
)
async def verify_2fa():
    return {"verified": True}
```

### 📱 Mobile API with Device Limits
```python
def extract_device_key(request: Request) -> str:
    """Rate limit by device fingerprint."""
    device_id = request.headers.get("Device-ID")
    app_version = request.headers.get("App-Version", "unknown")
    platform = request.headers.get("Platform", "unknown")
    
    if device_id:
        return f"device:{device_id}:{platform}:{app_version}"
    else:
        return f"ip:{request.client.host}"

@app.get("/api/mobile/sync")
@throttle(
    limit=100, ttl=3600,  # 100 syncs per hour per device
    key_type=KeyExtractionType.CUSTOM,
    key_extractor=extract_device_key
)
async def mobile_sync():
    return {"sync_data": "device-specific data"}
```

### 🤖 Bot Protection & Scraping Prevention
```python
def detect_bot(request: Request) -> bool:
    """Detect and allow verified bots."""
    user_agent = request.headers.get("User-Agent", "").lower()
    bot_token = request.headers.get("Bot-Token")
    
    # Allow verified search engine bots
    verified_bots = ["googlebot", "bingbot", "slurp"]
    if any(bot in user_agent for bot in verified_bots):
        return True
        
    # Allow bots with valid tokens
    return bot_token in os.getenv("VALID_BOT_TOKENS", "").split(",")

@app.get("/api/public-data")
@throttle(
    limit=10, ttl=60,  # Strict limits for non-bots
    bypass_function=detect_bot,
    key_type=KeyExtractionType.COMBINED,
    key_combination=["ip", "header:User-Agent"]
)
async def public_data():
    return {"data": "public information"}
```

## 🔧 Configuration Examples

### 🌍 Environment-Based Configuration
```python
import os
from fastrict import RateLimitStrategy, RateLimitStrategyName

def get_rate_limit_config():
    """Get rate limit configuration based on environment."""
    env = os.getenv("ENVIRONMENT", "development")
    
    if env == "production":
        return {
            "strategies": [
                RateLimitStrategy(name=RateLimitStrategyName.SHORT, limit=5, ttl=60),
                RateLimitStrategy(name=RateLimitStrategyName.MEDIUM, limit=50, ttl=600),
                RateLimitStrategy(name=RateLimitStrategyName.LONG, limit=500, ttl=3600),
            ],
            "redis_url": os.getenv("REDIS_URL"),
            "key_prefix": "prod_limits"
        }
    elif env == "staging":
        return {
            "strategies": [
                RateLimitStrategy(name=RateLimitStrategyName.SHORT, limit=10, ttl=60),
                RateLimitStrategy(name=RateLimitStrategyName.MEDIUM, limit=100, ttl=600),
                RateLimitStrategy(name=RateLimitStrategyName.LONG, limit=1000, ttl=3600),
            ],
            "redis_url": os.getenv("REDIS_URL", "redis://localhost:6379/1"),
            "key_prefix": "staging_limits"
        }
    else:  # development
        return {
            "strategies": [
                RateLimitStrategy(name=RateLimitStrategyName.SHORT, limit=100, ttl=60),
                RateLimitStrategy(name=RateLimitStrategyName.MEDIUM, limit=1000, ttl=600),
                RateLimitStrategy(name=RateLimitStrategyName.LONG, limit=10000, ttl=3600),
            ],
            "redis_url": "redis://localhost:6379/0",
            "key_prefix": "dev_limits"
        }

# Apply configuration
config = get_rate_limit_config()
repository = RedisRateLimitRepository.from_url(
    redis_url=config["redis_url"],
    key_prefix=config["key_prefix"]
)

app.add_middleware(
    RateLimitMiddleware,
    rate_limit_use_case=rate_limiter,
    default_strategies=config["strategies"],
    default_strategy_name=RateLimitStrategyName.MEDIUM
)
```

### 📋 Feature Flags Integration
```python
def feature_flag_bypass(request: Request) -> bool:
    """Bypass rate limiting based on feature flags."""
    # Integration with feature flag service
    user_id = request.headers.get("User-ID")
    
    if user_id:
        # Check if user has rate limiting bypass feature enabled
        return feature_flag_service.is_enabled(
            flag="rate_limiting_bypass", 
            user_id=user_id
        )
    return False

@app.get("/api/experimental")
@throttle(
    limit=10, ttl=300,
    bypass_function=feature_flag_bypass
)
async def experimental_feature():
    return {"feature": "experimental"}
```

## 🤝 Contributing

We welcome contributions! Fastrict is built with ❤️ by the community.

### 🚀 Quick Start for Contributors

```bash
# Fork and clone the repository
git clone https://github.com/yourusername/fastrict.git
cd fastrict

# Install development dependencies
pip install -e ".[dev]"

# Run tests
pytest

# Run linting
black src tests
flake8 src tests
mypy src

# Run the example
python src/examples/simple_example.py
```

### 📋 Contribution Guidelines

- **🐛 Bug Reports**: Use the issue tracker with detailed reproduction steps
- **✨ Feature Requests**: Propose new features with use cases
- **📝 Documentation**: Help improve our docs and examples
- **🧪 Tests**: Maintain 100% test coverage
- **🎨 Code Style**: Follow Ruff formatting and type hints

### 🏗️ Development Workflow

1. **Fork** the repository
2. **Create** a feature branch: `git checkout -b feature/amazing-feature`
3. **Make** your changes with tests
4. **Run** the test suite: `pytest --cov=fastrict`
5. **Commit** with clear messages: `git commit -m 'Add amazing feature'`
6. **Push** to your fork: `git push origin feature/amazing-feature`
7. **Create** a Pull Request

## 📚 Resources & Documentation

### 📖 Documentation
- **[API Reference](https://github.com/msameim181/fastrict)** - Complete API documentation
- **[User Guide](https://github.com/msameim181/fastrict)** - Step-by-step tutorials
- **[Examples](https://github.com/msameim181/fastrict/tree/main/examples)** - Real-world examples
- **[Architecture](https://github.com/msameim181/fastrict)** - Design decisions

### 🆘 Support Channels
- **🐛 [Issue Tracker](https://github.com/msameim181/fastrict/issues)** - Bug reports & feature requests
- **💬 [Discussions](https://github.com/msameim181/fastrict/discussions)** - Community Q&A
- **📧 [Email](mailto:9259samei@gmail.com)** - Direct support for enterprise users
- **💼 [LinkedIn](https://linkedin.com/in/msameim181)** - Professional inquiries

### 🔗 Related Projects
- **[FastAPI](https://fastapi.tiangolo.com/)** - Modern, fast web framework for building APIs
- **[Redis](https://redis.io/)** - In-memory data structure store  
- **[Starlette](https://www.starlette.io/)** - Lightweight ASGI framework
- **[Pydantic](https://pydantic-docs.helpmanual.io/)** - Data validation using Python type hints

## 📄 License

This project is licensed under the **MIT License** - see the [LICENSE](LICENSE) file for details.

## 📈 Changelog & Roadmap

### 🎯 Current Version: `v0.1.1`
See [CHANGELOG.md](CHANGELOG.md) for version history and release notes.

### 🚀 Upcoming Features
- **🌐 GraphQL Support**: Rate limiting for GraphQL endpoints
- **🌐 Django Support**: Rate limiting for Django applications
- **📊 Prometheus Metrics**: Built-in metrics collection
- **🔄 Circuit Breaker**: Integrate with circuit breaker patterns
- **🎯 Rate Limit Warming**: Gradual limit increases
- **📱 WebSocket Support**: Rate limiting for WebSocket connections

---

<div align="center">

**Fastrict - Powering the next generation of FastAPI applications**

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