SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b5dbb79968e49f000432d1cea0468e79703c96618929f44eb2359dd6f2c9b83d' 
  AND token = 'TuuqdNPJvigqq8DmgMpXd++KpYXJFwujn5X7uMsqazc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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