---
id: throttled-py
version: "3.4.1"
license: MIT
license_treatment: permissive
maintenance: active
---

# throttled-py — 🔧 High-performance Python rate limiting library with multiple algorithms (Fixed Window, Sliding Window, Token Bucket, Leaky Bucket & GCRA) and storage backends (Redis, In-Memory).

License: permissive · Maintenance: active · Downloads: 188.7K/mo

## What it is and what it does

throttled-py is a rate-limiting library that enforces quotas on request or operation rates using pluggable algorithms and storage backends. It provides five rate-limiting strategies—Fixed Window, Sliding Window, Token Bucket, Leaky Bucket, and GCRA—allowing you to choose the right algorithm for your use case. The library supports both synchronous and asynchronous code, and can store state in Redis (for distributed systems) or in-memory (for single-process applications).

You can apply rate limits via direct function calls, decorators, or context managers. The library returns detailed state information (remaining quota, reset time, retry-after) and can operate in immediate-response mode (reject when over quota) or wait-retry mode (pause until quota is available). Optional integrations include FastAPI middleware with IETF-compliant RateLimit headers, OpenTelemetry hooks, and MCP SDK support for AI model interactions.

Use it for:

- Protect API endpoints from abuse by enforcing per-user or per-IP request quotas with automatic 429 responses.
- Implement fair-share resource allocation in multi-tenant systems using Redis as a distributed quota store.
- Rate-limit background job workers or batch processes to prevent resource exhaustion.
- Add request throttling to async web scraping or API client code to respect rate limits.
- Enforce token budgets in AI model interactions via MCP SDK integration.
- Decorate database query functions to prevent query storms during traffic spikes.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Implements rate limiting with multiple algorithms (Fixed Window, Sliding Window, Token Bucket, Leaky Bucket, GCRA) and storage backends (Redis, In-Memory), supporting both sync and async code.

Yes. The library is actively maintained, has no security vulnerabilities, installs with zero runtime dependencies by default, and supports modern Python versions (3.10+). It offers a mature feature set with multiple algorithms and backends, making it suitable for both simple single-process rate limiting and complex distributed systems. The MIT license imposes no restrictions. Install it if you need flexible, performant rate limiting; skip it only if your use case is trivial or you require Python 3.8/3.9 support.

## Install

pip install throttled-py
uv add throttled-py
poetry add throttled-py

## Installing throttled-py

Before you install: Low friction: pure Python wheel with no runtime dependencies by default. Active maintenance with recent release (13 days ago) and 643 repository stars. Requires Python 3.10 or later.

License in practice: MIT license (permissive) allows unrestricted use, modification, and distribution with minimal obligations—suitable for commercial and proprietary projects.

Quickstart:

pip install throttled-py

from throttled import Throttled

throttle = Throttled(quota="1000/s burst 1000")
result = throttle.limit("key", cost=1)
print(result.limited)

Requires Python 3.10 or later; v3.x does not support Python 3.8 or 3.9.

Verify before relying:

- Whether Redis backend requires additional system setup or network configuration beyond the optional dependency.
- Performance characteristics of the Leaky Bucket and GCRA algorithms relative to Token Bucket in real-world workloads.
- Thread-safety guarantees for the In-Memory backend under high concurrency.

## Package facts

- License: MIT (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: active
- Downloads: 188.7K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

rate limiting library, token bucket algorithm, redis rate limiter, async rate limiting, request throttling, quota management, sliding window rate limit, leaky bucket algorithm, rate-limiting, quota-management, async-support

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