* For thread-safe usage, wrap with {@link java.util.Collections#synchronizedMap(Map)}:
 * </p>
 * <pre>
 * Map&lt;K, V&gt; syncMap = Collections.synchronizedMap(new LruHashMap&lt;&gt;(100));
 * </pre>
 * <p>
 * Alternatively, for high-concurrency scenarios, consider implementing a custom
 * LRU cache using {@link java.util.concurrent.ConcurrentHashMap} with an eviction strategy.
 * </p>
 *
 * @author koichik
 * @param <K> the key type

```bash
curl -X PUT "http://localhost:8080/api/admin/documents/bulk" \
  -H "Content-Type: application/x-ndjson" \
  -u admin:admin \
  --data-binary @documents.ndjson
```

#### Crawl-Based Migration

Alternatively, let Fess recrawl your content:

1. **Web Content**: Configure Web Crawler with starting URLs
2. **File Shares**: Configure File Crawler with SMB/FTP paths