SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '339bbb8ead9ad1b0234da26748699fc0d6590c72fc1384551c18c061444a945f' 
  AND token = '25XTHeZg7xLveHJVM83TxwwODMP8OvXwlUAa6StW/z8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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