SELECT 
  id_path 
FROM 
  cscart_categories 
WHERE 
  category_id IN (
    1, 16, 18, 20, 26, 27, 44, 48, 75, 100, 107, 
    237, 240, 241, 243, 249, 257, 261, 306
  )

Query time 0.00050

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_categories",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["category_id"],
      "rows": 19,
      "filtered": 100,
      "index_condition": "cscart_categories.category_id in (1,16,18,20,26,27,44,48,75,100,107,237,240,241,243,249,257,261,306)"
    }
  }
}