The Theory of Constraints or (ToC)[Google] is introduced in the book “The Goal“>The Goal” by Eli Goldratt. At its most basic level, the theory of constraints posits that there is only one thing right now preventing your team from going faster. It is the weakest/slowest link in a process or procedure.
How do you find that one thing? There are various possibilities depending on the sort of work environment. One way, that is appropriate to a manufacturing-like process is to identify the Work in Process (WIP) pileup. If you are working in a more human-skills based process, then ask “if you can only hire one skill set, what would it be?”
In an agile process framework like Scrum, there is constant discovery of the constraints (although possibly not the one specific constraint that is slowing the overall process). This discovery is encouraged by the Scrum Master and is exposed by team members as they participate in their daily “scrum” status meeting. An important feature of this meeting is that the team members identify any barriers to the performance of their work. The Scrum Master is then responsible for removing the barriers that are identified.
In organizations that are very paper-documentation oriented, often approval gates are one of the worst constraints in a process. Those who must approve the team’s movement to the next step must receive the documentation they need, then find the time to read it, then find the time to formulate their decision, and then find the time to communicate it to the team. I have been in environments where this can take a few months (I’m sure some organizations are worse, and many are better than this). During this time, the team is essentially idle.
Another typical problem exists in organizations that have gone through several rounds of layoffs in a short time period. In this situation, often the constraint is due to an unbalanced skill distribution. The organization may have very few people with a specific critical skill. The only way to remove the constraint (and speed up) is to add more people with the skill either by hiring or by training.
In general, because of their short iterations, and the resulting amplification of learning, agile teams tend to expose many constraints in the organizational environment. This can be a cause of backlash against the agile team.