Software Development Workflow with Queues

Below is an updated representation for the software development workflow. Note that Queue (Q) stages have been added in between the action stages.
Software Development Workflow with Queues

The sample Software Development Workflow revisited

Below are two figures: the first is from the  previous section representing the software development workflow (without Queue) snapshot. The second carries on the same example snapshot, but with the addition of  Queue stages. 

Software Development Workflow sample snapshot without Queues

Software Development Workflow sample snapshot with Queues

Here is a description for what is happening in each workflow stage for the software development workflow example without queues: Two requirements are in analysis. Three requirements are in development while two are being validated. One requirement is ready to release.
For the workflow without Queues,  even with cards parked under each stage, it is not clear which ones are actively being worked on. For instance, if you only have two people in this team, it is unlikely they are working on all the cards. How can we tell which ones are being worked on?
This is not the case for the workflow with Queues Note the distinction from the cards that are being worked on in action stages to the ones in Queue stages. Both workflow examples (with and without Queue) have the same number of cards. The workflow example with Queues explicitly shows which cards are active.

These could be workflows for real software development scenarios. For instance, these could be two versions of a card wall for the same team at a given moment. Consider a small Agile team with one analyst and three programmers. The programmers are able to work on design, coding, validation and deployment activities. The workflow with queue stages depicts a more realistic scenario. It tells you what is really under work, and what is still waiting for action. The current status of each activity is more precise. This is only one of the benefits from using Queue stages.