export interface BucketState {
    tokens: number;
    lastRefill: number;
}
export interface RateLimiterStore {
    get(key: string): Promise<BucketState | null>;
    set(key: string, state: BucketState): Promise<void>;
    /** Atomically consume tokens. When implemented, replaces get-then-set to prevent TOCTOU race conditions under concurrency. Returns null when the atomic operation could not be completed (caller should retry or fall back). */
    atomicConsume?(key: string, tokens: number, capacity: number, refillRate: number): Promise<ConsumeResult | null>;
}
export interface ConsumeResult {
    allowed: boolean;
    remaining: number;
    retryAfter?: number;
}
/** Token bucket rate limiter. Capacity = max tokens, refillRate = tokens added per second. */
export declare class RateLimiter {
    private store;
    private options;
    constructor(store: RateLimiterStore, options: {
        capacity: number;
        refillRate: number;
    });
    /** Consumes `tokens` for `key`. Returns allowed/denied with remaining count and optional retry delay. */
    consume(key: string, tokens?: number): Promise<ConsumeResult>;
}
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