/**
 * Leaky-bucket rate limiter.
 *
 * The bucket accumulates requests up to `capacity`. Water leaks out at a
 * constant `leakRate` requests/second — the effective steady-state rate.
 * When the bucket is full, incoming requests are rejected. Unlike
 * token-bucket, there is **no burst tolerance**: outgoing rate is
 * strictly bounded by `leakRate`.
 *
 * Use for traffic shaping and protecting downstream services with a hard
 * throughput ceiling (SMTP relays, upstream APIs with quota-per-second).
 * For user-facing endpoints, prefer `sliding` or `tokenBucket`.
 *
 * State encoding matches token-bucket: `"<level*1000>|<updatedAt>"`.
 * Writes go through the store's optional atomic `compareAndSet` when
 * available (bundled memory + Redis stores both provide it) so
 * concurrent requests can't race the level; stores without it fall
 * back to last-writer-wins `set`.
 *
 * @param {import('../index.js').BucketLimiterConfig} config
 * @returns {import('../index.js').Limiter}
 */
export function leakyBucket(config: import("../index.js").BucketLimiterConfig): import("../index.js").Limiter;