The Theory of Constraints was introduced by Eli goldratt. In 1984. In his book The goal, one of the biggest selling business books of all time, in the Theory of Constraints, throughput is defined as the rate at which a business process generates revenue, with the aim being to increase throughput and thus profitability, however, the throughput of a process is always limited by at least one constraint. And the Theory of Constraints provides tools to help identify and remove the constraints in a process. In this section, we cover the main elements of the Theory of Constraints and compare them with the with the lean philosophy. It is as we will discover all about flow