/**
 * SQLite-backed implementation of the photon-core `MemoryBackend` interface.
 *
 * Each resolved namespace (typically a per-photon memory directory) gets its
 * own SQLite database at `{namespace}/.kv.sqlite` with a single `kv(key, value)`
 * table. Within a namespace, reads use a single SELECT and writes use
 * INSERT...ON CONFLICT UPDATE; range scans (`list(prefix)`) use a B-tree index
 * scan instead of a full directory walk.
 *
 * Opt-in: not installed by default. Consumers swap it in via
 * `setDefaultMemoryBackend(new SqliteMemoryBackend())` from `@portel/photon-core`.
 * Under Bun the backend uses `bun:sqlite` (zero install); under Node it falls
 * back to `better-sqlite3` via `./sqlite-runtime.ts`.
 */
import type { MemoryBackend } from '@portel/photon-core';
export declare class SqliteMemoryBackend implements MemoryBackend {
    private dbs;
    private updateLocks;
    private openDb;
    private withUpdateLock;
    get(namespace: string, key: string): Promise<unknown>;
    set(namespace: string, key: string, value: any): Promise<void>;
    delete(namespace: string, key: string): Promise<boolean>;
    has(namespace: string, key: string): Promise<boolean>;
    keys(namespace: string): Promise<string[]>;
    clear(namespace: string): Promise<void>;
    update(namespace: string, key: string, updater: (current: unknown) => unknown): Promise<unknown>;
    list(namespace: string, prefix?: string): Promise<Array<{
        key: string;
        value: any;
    }>>;
    /**
     * Close all open database handles. Call during shutdown or between tests.
     */
    close(): Promise<void>;
}
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