SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5230854097ea1ffdda019e5b91dac766de22a59da6dfe83cf51e8a1d91ab4844' 
  AND token = '8qdFD8DTPk6tt6GjTfk5GtB86XwlpBedZt5oLcOB+ak=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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