import asyncio
import time
from collections import defaultdict

_buckets: dict[str, list[float]] = defaultdict(list)
_lock = asyncio.Lock()


async def is_rate_limited(key: str, max_requests: int, window_seconds: int) -> bool:
    """Returns True if request should be blocked (limit exceeded)."""
    async with _lock:
        now = time.monotonic()
        cutoff = now - window_seconds
        _buckets[key] = [t for t in _buckets[key] if t > cutoff]
        if len(_buckets[key]) >= max_requests:
            return True
        _buckets[key].append(now)
        return False