import { OptimizationResult } from '../types/ai';
/**
 * Simple LRU + TTL cache for AI optimization results.
 * The cache key is derived from the SQL text (with literals masked)
 * so structurally identical queries hit the same entry.
 */
export declare class AiCache {
    private store;
    private readonly ttlMs;
    private readonly maxEntries;
    constructor(ttlMs?: number, maxEntries?: number);
    private makeKey;
    get(sql: string): OptimizationResult | null;
    set(sql: string, result: OptimizationResult): void;
    clear(): void;
    get size(): number;
}
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