SELECT 
  usergroup 
FROM 
  cscart_usergroup_descriptions 
WHERE 
  usergroup_id = 1 
  AND lang_code = 'vi'

Query time 0.00029

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}