SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    308, 293, 304, 306, 295, 294, 311, 297, 
    310, 301, 303, 309, 299, 302, 292, 305, 
    166, 203, 219
  ) 
  AND category_id != 264

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.02230529,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_categories",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "parent", "p_category_id"],
          "key": "parent",
          "key_length": "3",
          "used_key_parts": ["parent_id"],
          "loops": 1,
          "rows": 34,
          "cost": 0.02230529,
          "filtered": 100,
          "attached_condition": "cscart_categories.parent_id in (308,293,304,306,295,294,311,297,310,301,303,309,299,302,292,305,166,203,219) and cscart_categories.category_id <> 264",
          "using_index": true
        }
      }
    ]
  }
}