SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8b81b45521258012ddaf933b061f3d205d8a4adbe0d8fde4d38ce5b326086fc' 
  AND token = '+/L4KCAzRxI55MKlvzVAgvl29JDc3yonG7hpTY7rhbU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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