SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'fe39cecb81f1ec4d61bf3468f729819144aa840c94e3172c1f665c285b86a67c' 
  AND token = '7MTZlgr9jtxMrkjBOfFQDdd+FyqfF9VAtjOrieyzhr4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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