/**
 * Size and keyspace aggregates for INFO and MEMORY introspection.
 */
import type Database from './driver.ts';
export declare function createUsageStorage(db: Database): {
    /** Bytes of key name plus stored payload (fields, members, items, scores). */
    keyBytes(key: Buffer, type: number): number;
    /** Keys with a future expiration and their mean remaining TTL in ms. */
    expiring(now: number): {
        count: number;
        avgTtlMs: number;
    };
    /** SQLite main database size in bytes (excludes WAL). */
    databaseBytes(): number;
};