SELECT 
  * 
FROM 
  cscart_csc_virtual_categories_conditions 
  LEFT JOIN cscart_category_descriptions ON cscart_category_descriptions.category_id = cscart_csc_virtual_categories_conditions.category_id 
WHERE 
  cscart_csc_virtual_categories_conditions.is_virtual = 'Y' 
  AND cscart_category_descriptions.lang_code = 'ru' 
ORDER BY 
  category

Query time 0.00064

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "cscart_category_descriptions.category",
      "temporary_table": {
        "table": {
          "table_name": "cscart_csc_virtual_categories_conditions",
          "access_type": "ALL",
          "possible_keys": ["PRIMARY"],
          "rows": 400,
          "filtered": 100,
          "attached_condition": "cscart_csc_virtual_categories_conditions.is_virtual = 'Y'"
        },
        "table": {
          "table_name": "cscart_category_descriptions",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["category_id", "lang_code"],
          "ref": [
            "devmotorsbay.cscart_csc_virtual_categories_conditions.category_id",
            "const"
          ],
          "rows": 1,
          "filtered": 100,
          "index_condition": "cscart_category_descriptions.lang_code = 'ru' and cscart_category_descriptions.category_id = cscart_csc_virtual_categories_conditions.category_id"
        }
      }
    }
  }
}