A bottleneck in process and software development is a part in a chain of process. A bottleneck is the part that reduce the process capacity and controls the flow in the system. A bottleneck isn’t always a problem, because all process have a internal or external bottleneck but you should know where it is.
It could be an temporary or something that´s been a problem for long time. Because their is a least one bottleneck in all process its important to find it. When you find a process constraint it is easier to adjust the process flow to match the bottleneck “or weakest link in the chain”. If you put in to much it will start to pileup a queue. And after the bottleneck it is risk for “starving” because not enough is flowing through.
Another consequence is stall in production, supply overstock or to low throughput. But putting in more resources in the process do not help and instead risk to break the system. So try to find the bottleneck to see if there is anything that´s reducing they capacity.
One way to find bottleneck is to use the method Kanban and measure how things flow through the system. When an problem is found in the system the organization can start to focus on fixing the problem.
Bottlenecks in a process can be hardware, planing, individuals, processes, competence or something else that reduce the overall capacity in the process. So when a bottleneck is find it is time to get to the problems root cause. Don´t fix the symptoms of the bottleneck instead go to bottom of the problem.