https://techcrunch.com/2018/07/13/instacart-taps-postmates-to-help-with-deliveries-in-sf-during-peak-demand/

Instacart has tapped Postmates to offer better delivery services during peak hours in a San Francisco pilot.

While Instacart will still handle all the shopping for its customers, it will hand off some deliveries to Postmates at times when there is high demand on the Instacart platform.