PyrateLimiter is a fast, async-friendly rate limiter for Python -- Leaky-Bucket
algorithm with pluggable backends.

Features:
- Leaky-bucket algorithm: smooth, well-understood rate limiting.
- Multiple rates at once: e.g. 5/second and 1000/hour on the same key.
- Per-key limits: track different services, users, or resources independently.
- Pluggable backends: in-memory, SQLite, Redis (sync and async), Postgres, and
  multiprocessing.
- Sync & async: the same API works in both; async paths never block the event
  loop.
- Direct calls or decorators: limiter.try_acquire(...) or
  @limiter.as_decorator(...).
- Blocking or non-blocking: wait for a permit (with optional timeout) or fail
  fast.