SELECT 
  * 
FROM 
  cscart_menus 
  LEFT JOIN cscart_menus_descriptions ON cscart_menus.menu_id = cscart_menus_descriptions.menu_id 
WHERE 
  cscart_menus_descriptions.lang_code = 'ja' 
  AND cscart_menus.company_id = 2 
  AND cscart_menus.menu_id = 5 
  AND cscart_menus.company_id = 2

Query time 0.00028

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_menus",
      "access_type": "const",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["menu_id"],
      "ref": ["const"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_menus_descriptions",
      "access_type": "const",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["menu_id", "lang_code"],
      "ref": ["const", "const"],
      "rows": 1,
      "filtered": 100
    }
  }
}