import { Database } from './db/index.js';
declare class PromiseQueue {
    private tail;
    private pending;
    private idleWaiters;
    add(task: () => Promise<void>): void;
    onIdle(): Promise<void>;
}
export declare class BackgroundQueue {
    db: Database;
    queue: PromiseQueue;
    destroyed: boolean;
    constructor(db: Database);
    add(task: Task): void;
    processAll(): Promise<void>;
    destroy(): Promise<void>;
}
type Task = (db: Database) => Promise<void>;
export {};