/**
 * Per-node in-memory token-bucket rate limiter (#163).
 *
 * Deliberately PER-NODE, not replicated: Harper replication makes a shared
 * counter table a hot-write anti-pattern, and the surfaces this limits are
 * already bounded cross-node — the client_credentials grant by the assertion
 * replay guard and its ≤60s `exp` window, CIMD fetches by the concurrency
 * caps. A node-local bucket is the right defense-in-depth without turning
 * every token request into a replicated write.
 *
 * Buckets refill continuously (elapsed-time based — no interval timers), so a
 * limit of N/min admits a burst of up to N and then one request per 60/N
 * seconds. Keys may be ATTACKER-CHOSEN strings (client_ids, URLs), so: (1) the
 * key space is LRU-bounded — at `maxKeys` the least-recently-used bucket is
 * evicted (an evicted bucket forgets that key's spend history, acceptable
 * because eviction requires `maxKeys` distinct keys inside one window and the
 * global concurrency caps still bound aggregate work); and (2) the key is
 * stored as a fixed-size SHA-256 fingerprint, so a flood of long distinct keys
 * bounds map memory to `maxKeys` × a constant, not × the raw key length.
 */
export type RateLimitResult = {
    allowed: true;
} | {
    allowed: false;
    retryAfterSeconds: number;
};
export type RateLimiter = {
    tryTake(key: string): RateLimitResult;
    /** Drop all bucket state (for testing). @internal */
    _reset(): void;
};
export declare function createRateLimiter(options: {
    /** Bucket capacity (maximum burst). */
    capacity: number;
    /** Continuous refill rate, tokens per minute. */
    refillPerMinute: number;
    /** LRU bound on distinct keys tracked. Default 10 000. */
    maxKeys?: number;
    /** Clock override (for testing). Default Date.now. */
    now?: () => number;
}): RateLimiter;