The Hidden Costs of Queues in Product Development

In product development and process management, queues can silently become a significant source of economic waste. Queues delay progress, reduce efficiency, and create ripple effects that harm quality, motivation, and ultimately, business outcomes. This article explores seven critical forms of waste that queues generate: idle capacity, longer cycle times, increased risk, greater variability, more overhead, lower quality, and diminished motivation.

The Hidden Costs of Queues

1. Idle Capacity

Queues can create idle capacity in a system when workers or resources are waiting for the next task. For example, if a downstream team is bottlenecked by a large queue, upstream teams may find themselves with nothing to work on, leading to wasted time and resources (see Principle Q8. The Principle of Linked Queues: Adjacent Queues See Arrival or Service Variability Depending on Loading for more details). This mismatch in queue capacity leads to inefficiencies where some teams are overloaded, while others are left underutilized. The result is a misallocation of resources that can drive up costs and reduce overall productivity.

2. Longer Cycle Time

The most apparent consequence of queues is the increased time it takes to complete work. When a line or queue grows longer, so does the wait to reach the front. In economic terms, the cost of delay typically rises in proportion to the queue size. As each task, project, or product waits longer in the queue, it delays value delivery to the customer, leading to greater opportunity costs.

3. Increased Risk

As queues grow, so does the transit time through the product development pipeline. The longer it takes to bring a product to market, the greater the risk that customer preferences will shift, a competitor will preempt your offering, or the underlying technology will evolve. In essence, long queues make organizations more vulnerable to external changes, increasing the chance of delivering an outdated or irrelevant product.

4. More Variability

High levels of utilization tend to amplify variability. When systems are overloaded, the variability in process times, quality, and throughput becomes more pronounced. In a queueing system, the more loaded the system, the more unpredictable the flow of work becomes, leading to further inefficiencies and increased difficulty in planning.

5. More Overhead

The more projects you have in process, the more effort is required to track and report on their progress. This creates additional overhead, as teams must spend time updating managers and stakeholders on the status of each project. Worse yet, long queues mean that managers often demand more frequent updates, exacerbating the burden on teams. The result is a cycle of status reporting that detracts from the actual work that moves projects forward.

6. Lower Quality

Queues also erode the quality of work by delaying feedback from downstream processes. When feedback is delayed, errors and flawed assumptions can persist for longer periods, embedding problems deeper into the product. For example, if a programmer makes an incorrect assumption but must wait 30 days for feedback, that incorrect assumption might propagate through 30 days of code, multiplying the scope of the issue. Thus, the cost of errors increases with queue length.

7. Less Motivation

Finally, queues undermine motivation. When the next process in the workflow is heavily backlogged, there’s little incentive to rush to complete your current task. This phenomenon is explained by Parkinson’s Law, which states that work expands to fill the time available for its completion. If workers know that their efforts will be stuck in a queue, they have less motivation to be productive, which can lead to procrastination and reduced overall output.

Conclusion

The economic waste created by queues is both significant and varied. From longer cycle times and increased risks to reduced quality and team motivation, the impact of queues can be felt across all areas of product development and delivery. To reduce this waste, organizations must focus on minimizing queues by optimizing workflows, improving feedback loops, and ensuring that projects don't languish in the system unnecessarily. By doing so, they can accelerate time to market, reduce costs, and boost overall efficiency.

Check the section Managing Queues for more insights on how to minimize the negative effects of queues in product development.

Based on the book The Principles of Product Development Flow by Donald G. Reinertsen.