/**
 * Batches many GC registrations behind a single shared timeout.
 */
export declare class CleanupQueue {
    private static instance;
    private tasks;
    private timeoutId;
    private microtaskScheduled;
    private constructor();
    static getInstance(): CleanupQueue;
    /**
     * Queues a cleanup task and defers timeout selection to a microtask so
     * multiple synchronous registrations can share one root timer.
     */
    schedule(key: unknown, gcTime: number, callback: () => void): void;
    cancel(key: unknown): void;
    /**
     * Keeps only one active timeout: whichever task is due next.
     */
    private updateTimeout;
    /**
     * Runs every task whose deadline has passed, then schedules the next wakeup
     * if there is still pending work.
     */
    private process;
    /**
     * Resets the singleton instance for tests.
     */
    static resetInstance(): void;
}