title: RateLimiter
description: Redis-backed distributed rate limiting with GCRA algorithm in JustAPI.
keywords: [JustAPI, rate limiter, GCRA, Redis, distributed rate limiting]

Create Rate Limiter

from justapi import RateLimiter

# Async — creates Redis connection
limiter = await RateLimiter.new_redis("redis://localhost:6379")

Check Rate Limit

result = await limiter.check_limit(
    key="user:123",        # unique key per user/client
    capacity=100,          # max requests in window
    replenish_rate=10,     # tokens added per second
    tokens=1,              # tokens to consume
)

if result.allowed:
    # Process request
    return {"status": "ok"}
else:
    # Rate limited
    return JSONResponse(
        status_code=429,
        content={"error": "Rate limit exceeded"},
        headers={"Retry-After": str(result.retry_after_ms // 1000)},
    )

Parameters

RateLimitResult

Built-in Middleware

JustAPI also provides a built-in rate limiter middleware:

app.add_middleware(
    RateLimiter,
    capacity=100,
    replenish_rate=10,
)

See Also

• Resilience Patterns — circuit breakers, retry
• Security — authentication