/**
 * Simple in-memory sliding-window rate limiter for login throttling.
 */
export declare class MemoryRateLimiter {
    private readonly attempts;
    /**
     * @param key - Unique throttle key (e.g. IP + email).
     * @param maxAttempts - Maximum attempts allowed in the window.
     * @returns True when the key is locked out.
     */
    tooManyAttempts(key: string, maxAttempts: number): boolean;
    /**
     * @param key - Throttle key.
     * @param decaySeconds - Window length in seconds.
     */
    hit(key: string, decaySeconds: number): void;
    /**
     * Clears attempts for a key after successful login.
     *
     * @param key - Throttle key.
     */
    clear(key: string): void;
    /**
     * @param key - Throttle key.
     * @returns Seconds until retry, or 0 when not locked.
     */
    availableIn(key: string): number;
}
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