SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    343, 344, 168, 169, 170, 175, 171, 172, 
    173, 341, 342, 174, 176, 3352
  )

Query time 0.00016

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_categories",
      "access_type": "range",
      "possible_keys": ["parent"],
      "key": "parent",
      "key_length": "3",
      "used_key_parts": ["parent_id"],
      "rows": 14,
      "filtered": 100,
      "index_condition": "cscart_categories.parent_id in (343,344,168,169,170,175,171,172,173,341,342,174,176,3352)"
    }
  }
}