Abstract: Embodiments herein describe a robotic pick and stow storage system with a built-in consolidation function that increases the storage density. The system can include a stowing robot, a consolidation robot, and individual containers. The stowing robot may pick an item, identify a free space in the container large enough for the item, and then place the item in the free space. The items placed in the container may have a space between it and a neighboring item or items (referred to herein as a stow buffer) due to uncertainties or inaccuracies in the stowing process. The embodiments herein describe a stow and consolidation action that reduces the stow buffers thereby providing additional space in the container for more items. The consolidation robot can tilt and vibrate the container such that the items move closer together thereby generating free space for additional items in the container.