SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '96da708fc27226ce03c095883a7c4c1d51ed975c50e6e3e60471f6fa710c50c8' 
  AND token = 'xnDQADvTzc5ZdPHZ5YNuj9LK3clQJFZzTiXJF0/aGkI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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