}
        return numOfDeleted;
    }

    /**
     * Refreshes the specified index to make recent changes visible for search.
     * This operation ensures that all pending writes are persisted and searchable.
     *
     * @param searchEngineClient the search engine client to use for refresh
     * @param index the index name to refresh
     * @return the refresh status code
     */

**DataService**: Access result persistence, iteration

**Implementations**:
- `UrlQueueServiceImpl`, `DataServiceImpl`: In-memory (default)
- `OpenSearchDataService`: OpenSearch backend (persistent)

### Processing Pipeline

```
CrawlerThread → Client → ResponseProcessor → Transformer → Extractor → ExtractData
                                                                            ↓