export type SendFailure = {
    app_id: string;
    category: string;
    reason: string;
    failures: number;
    first_at: Date;
    last_at: Date;
};
export declare function recordSendFailure(appId: string, category: string, reason: string): Promise<void>;
export declare function readSendFailures(appIdCategories: string[]): Promise<Map<string, SendFailure>>;
export declare function pruneSendFailures(): Promise<void>;
