export interface CacheConfig {
    /** Enable/disable caching. Default: true */
    enabled?: boolean;
    /**
     * Max entries per resolver cache namespace. Default: 100_000.
     * Set to 0 to disable the resolver cache explicitly.
     */
    maxSize?: number;
    /** DNS result TTL in ms. Default: 1_440_000 (24 min) */
    dnsTtl?: number;
}
/**
 * In-memory LRU cache with TTL-based expiry and size-based eviction.
 * Uses Map insertion order for O(1) LRU tracking.
 * Unlike `CacheConfig.maxSize`, this standalone utility requires a positive
 * capacity; construct no cache when storage must be disabled.
 */
export declare class LruCache<T = any> {
    private cache;
    private readonly maxSize;
    constructor(maxSize?: number);
    /** Get a value by key. Returns undefined if missing or expired. Promotes to MRU on hit. */
    get(key: string): T | undefined;
    /** Set a value with a TTL in milliseconds. TTL 0 expires immediately. Evicts LRU at capacity. */
    set(key: string, data: T, ttlMs: number): void;
    /** Check if a key exists and is not expired. */
    has(key: string): boolean;
    /** Delete a specific key. Returns true if the key existed. */
    delete(key: string): boolean;
    /** Remove all entries. */
    clear(): void;
    /** Number of entries (including potentially expired ones not yet evicted). */
    get size(): number;
    /** Iterate all non-expired keys. Lazily evicts expired entries. */
    keys(): IterableIterator<string>;
    /** Iterate all non-expired values. Lazily evicts expired entries. */
    values(): IterableIterator<T>;
    /** Iterate all non-expired [key, value] pairs. Lazily evicts expired entries. */
    entries(): IterableIterator<[string, T]>;
    /** Purge all expired entries. Returns number of entries removed. */
    prune(): number;
    /** Peek at a value without promoting it in the LRU order. */
    peek(key: string): T | undefined;
    /** Get remaining TTL in ms for a key. Returns 0 if missing or expired. */
    ttl(key: string): number;
}