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Hishel

Elegant HTTP Caching for Python

Hishel (հիշել, to remember in Armenian) is a modern HTTP caching library for Python that implements RFC 9111 specifications. It provides seamless caching integration for popular HTTP clients with minimal code changes.

✨ Features

🎯 RFC 9111 Compliant - Fully compliant with the latest HTTP caching specification
🔌 Easy Integration - Drop-in support for HTTPX, Requests, ASGI, FastAPI, and BlackSheep
💾 Flexible Storage - SQLite backend with more coming soon
⚡ High Performance - Efficient caching with minimal overhead
🔄 Async & Sync - Full support for both synchronous and asynchronous workflows
🎨 Type Safe - Fully typed with comprehensive type hints
🧪 Well Tested - Extensive test coverage and battle-tested
🎛️ Configurable - Fine-grained control over caching behavior with flexible policies
💨 Memory Efficient - Streaming support prevents loading large payloads into memory
🌐 Universal - Works with any ASGI application (Starlette, Litestar, BlackSheep, etc.)
🎯 GraphQL Support - Cache GraphQL queries with body-sensitive content caching

📦 Installation

pip install hishel

Optional Dependencies

Install with specific integration support:

pip install hishel[httpx]      # For HTTPX support
pip install hishel[requests]   # For Requests support
pip install hishel[fastapi]    # For FastAPI support (includes ASGI)

Or install multiple:

pip install hishel[httpx,requests,fastapi]

Note

ASGI middleware has no extra dependencies - it's included in the base installation.

🚀 Quick Start

With HTTPX

Synchronous:

from hishel.httpx import SyncCacheClient

client = SyncCacheClient()

# First request - fetches from origin
response = client.get("https://api.example.com/data")
print(response.extensions["hishel_from_cache"])  # False

# Second request - served from cache
response = client.get("https://api.example.com/data")
print(response.extensions["hishel_from_cache"])  # True

Asynchronous:

from hishel.httpx import AsyncCacheClient

async with AsyncCacheClient() as client:
    # First request - fetches from origin
    response = await client.get("https://api.example.com/data")
    print(response.extensions["hishel_from_cache"])  # False

    # Second request - served from cache
    response = await client.get("https://api.example.com/data")
    print(response.extensions["hishel_from_cache"])  # True

With Requests

import requests
from hishel.requests import CacheAdapter

session = requests.Session()
session.mount("https://", CacheAdapter())
session.mount("http://", CacheAdapter())

# First request - fetches from origin
response = session.get("https://api.example.com/data")

# Second request - served from cache
response = session.get("https://api.example.com/data")
print(response.headers.get("X-Hishel-From-Cache"))  # "True"

With ASGI Applications

Add caching middleware to any ASGI application:

from hishel.asgi import ASGICacheMiddleware

# Wrap your ASGI app
app = ASGICacheMiddleware(app)

# Or configure with options
from hishel import AsyncSqliteStorage, CacheOptions, SpecificationPolicy

app = ASGICacheMiddleware(
    app,
    storage=AsyncSqliteStorage(),
    policy=SpecificationPolicy(
      cache_options=CacheOptions(shared=True)
    )
)

With FastAPI

Add Cache-Control headers using the cache() dependency:

from fastapi import FastAPI
from hishel.fastapi import cache

app = FastAPI()

@app.get("/api/data", dependencies=[cache(max_age=300, public=True)])
async def get_data():
    # Cache-Control: public, max-age=300
    return {"data": "cached for 5 minutes"}

# Optionally wrap with ASGI middleware for local caching according to specified rules
from hishel.asgi import ASGICacheMiddleware
from hishel import AsyncSqliteStorage

app = ASGICacheMiddleware(app, storage=AsyncSqliteStorage())

With BlackSheep

Use BlackSheep's native cache_control decorator with Hishel's ASGI middleware:

from blacksheep import Application, get
from blacksheep.server.headers.cache import cache_control

app = Application()

@get("/api/data")
@cache_control(max_age=300, public=True)
async def get_data():
    # Cache-Control: public, max-age=300
    return {"data": "cached for 5 minutes"}

🎛️ Advanced Configuration

Caching Policies

Hishel supports two types of caching policies for flexible caching strategies:

SpecificationPolicy (RFC 9111 Compliant)

The default policy that follows HTTP caching standards:

from hishel import CacheOptions, SpecificationPolicy
from hishel.httpx import SyncCacheClient

client = SyncCacheClient(
    policy=SpecificationPolicy(
      cache_options=CacheOptions(
          shared=False,                              # Use as private cache (browser-like)
          supported_methods=["GET", "HEAD", "POST"], # Cache GET, HEAD, and POST
          allow_stale=True                           # Allow serving stale responses
      )
    )
)

FilterPolicy (Custom Filtering)

Apply custom logic to determine what gets cached:

from hishel import FilterPolicy, BaseFilter, Request
from hishel.httpx import AsyncCacheClient

class CacheOnlyAPIRequests(BaseFilter[Request]):
    def needs_body(self) -> bool:
        return False

    def apply(self, item: Request, body: bytes | None) -> bool:
        # Only cache requests to /api/ endpoints
        return "/api/" in str(item.url)

client = AsyncCacheClient(
    policy=FilterPolicy(
        request_filters=[CacheOnlyAPIRequests()]
    )
)

Learn More

See the Policies Guide for detailed examples including GraphQL caching, body inspection, and combining multiple filters.

Custom Storage Backend

from hishel import SyncSqliteStorage
from hishel.httpx import SyncCacheClient

storage = SyncSqliteStorage(
    database_path="my_cache.db",
    default_ttl=7200.0,           # Cache entries expire after 2 hours
    refresh_ttl_on_access=True    # Reset TTL when accessing cached entries
)

client = SyncCacheClient(storage=storage)

GraphQL and Body-Sensitive Caching

Cache GraphQL queries and other POST requests by including the request body in the cache key.

Using per-request header:

from hishel.httpx import SyncCacheClient

client = SyncCacheClient()

# Cache GraphQL queries - different queries get different cache entries
graphql_query = """
    query GetUser($id: ID!) {
        user(id: $id) {
            name
            email
        }
    }
"""

response = client.post(
    "https://api.example.com/graphql",
    json={"query": graphql_query, "variables": {"id": "123"}},
    headers={"X-Hishel-Body-Key": "true"}  # Enable body-based caching
)

# Different query will be cached separately
response = client.post(
    "https://api.example.com/graphql",
    json={"query": graphql_query, "variables": {"id": "456"}},
    headers={"X-Hishel-Body-Key": "true"}
)

Using global configuration:

from hishel.httpx import SyncCacheClient
from hishel import FilterPolicy

# Enable body-based caching for all requests
client = SyncCacheClient(policy=FilterPolicy(use_body_key=True))

# All POST requests automatically include body in cache key
response = client.post(
    "https://api.example.com/graphql",
    json={"query": graphql_query, "variables": {"id": "123"}}
)

🏗️ Architecture

Hishel uses a sans-I/O state machine architecture that separates HTTP caching logic from I/O operations:

✅ Correct - Fully RFC 9111 compliant
✅ Testable - Easy to test without network dependencies
✅ Flexible - Works with any HTTP client or server
✅ Type Safe - Clear state transitions with full type hints

🔮 Roadmap

We're actively working on:

🎯 Performance optimizations
🎯 More integrations
🎯 Partial responses support

📚 Documentation

Comprehensive documentation is available at https://hishel.com/dev

🤝 Contributing

Contributions are welcome! Please feel free to submit a Pull Request. For major changes, please open an issue first to discuss what you would like to change.

See our Contributing Guide for more details.

📄 License

This project is licensed under the BSD-3-Clause License - see the LICENSE file for details.

💖 Support

If you find Hishel useful, please consider:

⭐ Starring the repository
🐛 Reporting bugs and issues
💡 Suggesting new features
📖 Improving documentation
☕ Buying me a coffee

🙏 Acknowledgments

Hishel is inspired by and builds upon the excellent work in the Python HTTP ecosystem, particularly:

HTTPX - A next-generation HTTP client for Python
Requests - The classic HTTP library for Python
RFC 9111 - HTTP Caching specification

Made with ❤️ by Kar Petrosyan