SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '2a80a5b7a48b0de5656f528dd168e4499c96be9da018e3c3046fa936e3938532' 
  AND token = 'r/d9JSguoqdcvAv6NatWGYxVdCaScZaZBrIzMg6qT8Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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