SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a786f557277c47ca516a281994b24182f10a24807adf8cf1bd020848d42db4dc' 
  AND token = 'i8E+3NvcmOkw+i/Oh0STrKQ/beM9mHtgi1vQ50tulzY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}