export declare class FileCache {
    private readonly baseDir;
    private readonly inflight;
    constructor(baseDir?: string);
    get<T>(key: string, ttlMs?: number): Promise<T | undefined>;
    set<T>(key: string, data: T): Promise<void>;
    /**
     * Returns cached value if present, otherwise calls fetchFn and caches the result.
     * Results that are null or undefined are NOT cached, so subsequent calls will retry.
     * Concurrent calls for the same key share a single fetchFn invocation.
     */
    getOrFetch<T>(key: string, ttlMs: number | undefined, fetchFn: () => Promise<T>): Promise<T>;
    private filePath;
}