While it is true that maltodextrin is a "complex" carb, it is so only in "title".
A complex carbohydrate refers to many monosaccharide units linked together. In addition, you will often hear the terms “long”, and “short” carbohydrate chains. Short carbohydrate chains are those under 10 sugar molecules. And long chains are those over 10 sugar molecules.
It is an easily digested carbohydrate made from cornstarch. The starch is cooked, and then acid and/or enzymes are used to break the starch into smaller chains (3-20 chains in maltodextrin). These chains are composed of several dextrose molecules held together by very weak hydrogen bonds. These are very weak bonds and are easily broken down, so it is digested nearly as fast as dextrose.