Architecting for sustainability: a re:Invent 2021 recap

At AWS re:Invent 2021, we announced the AWS Well-Architected Sustainability Pillar, which marks sustainability as a key pillar of building workloads to best deliver on business need. In session ARC325 – Architecting for Sustainability, Adrian Cockcroft, Steffen Grunwald, and Drew Engelson (Director of Engineering at Starbucks) gave a detailed explanation of what to expect from the Sustainability Pillar whitepaper and how Starbucks has applied AWS best practices to their workloads.

AWS is committed to building a sustainable business for our customers and the planet. Amazon co-founded The Climate Pledge in 2019, committing to reach net-zero carbon by the Year 2040 — 10 years ahead of the Paris Agreement. As part of reaching our commitment, Amazon is on a path to powering our operations with 100% renewable energy by 2025 — 5 years ahead of our original target of 2030.

In 2020, we became the world’s largest corporate purchaser of renewable energy, reaching 65% renewable energy across our business. Amazon also continues to invest in renewable energy projects paired with energy storage: the energy storage systems allow Amazon to store clean energy produced by its solar projects and deploy it when solar energy is unavailable, such as in the evening hours, or during periods of high demand. This strengthens the climate impact of Amazon’s clean energy portfolio by enabling carbon-free electricity throughout more parts of the day.

As customers architect solutions with AWS services to fulfill their business needs, they also influence the sustainability of a workload. AWS had published five pillars in the AWS Well-Architected Framework that capture best practices for operational excellence, security, reliability, performance, and cost of workloads. These pillars have supported the business need for faster time-to-value for features and the delivery of products.

In light of the climate crisis, we have a new challenge to help businesses optimize their application architectures and workloads for sustainability. With sustainability as the sixth pillar in the AWS Well-Architected Framework, builders have guidance to optimize their workloads for energy reduction and efficiency improvement across all components of a workload.

How Starbucks is reducing their footprint

Starbucks has set very ambitious sustainability goals to reduce the environmental impact of their business. As Drew Engelson mentioned in his presentation, there was a gap between these major goals and how members of the technology teams could participate in this mission. Drew decided to evaluate the systems his team was responsible for and initiated an internal framework for understanding the environmental impact of the systems.

Sustainability proxy metrics based on service usage, as demonstrated in the AWS Well-Architected Lab for Sustainability, complemented AWS customer carbon footprint tool data to help the team drive reductions. The goal was to snap a baseline and identify areas for further optimization. The Starbucks team applied the Well-Architected Sustainability Pillar best practices after performing an AWS Well-Architected review early in the process.

Through working with AWS, Starbucks saw that from 2019 to 2020, the actual carbon footprint of their AWS workloads was reduced by approximately 32%, despite tremendous business growth during that same period. The customer carbon footprint tool indicates that these systems’ carbon footprint was further reduced by 50% in subsequent quarters.

Optimizing beyond cost

The Starbucks team already optimized their workloads for cost efficiency, leading to high energy and resource efficiency. Starbucks relies heavily on Kubernetes, which allows them to densely pack their services onto the underlying infrastructure, yielding very high utilization. Binary protocols, like gRPC, are used for efficient communication between microservices. This also cuts down on the data transfer between different networks. Many of their services are written in efficient Scala code, which adds another layer of optimization to the workload.

By taking a data-driven approach, Drew and his team at Starbucks also were able to review scaling thresholds. Based on data, they were able to adjust the auto scaling curve much more closely and smoothly, matching the actual demand curve and reducing the resources they needed to provision.

Drew’s team went beyond the initial optimization cost-benefits to sustainability of the whole stack. They identified workloads suitable for Amazon EC2 Spot Instances to leverage unused, on-demand capacity and increase the overall resource utilization of the cloud. The Starbucks team is starting to examine the impact of their mobile application to end-user devices, and they are taking steps to reduce the downstream impacts: for example, considering the size of client-side scripts, devices’ CPU usage, and color scheme (dark mode reduces the energy required for certain display types).

Starbucks takes optimization for sustainability seriously—so seriously that they coined the term “TCO₂”, which highlights the importance climate impact when measuring Total Costs of Ownership (Figure). Drew raised an important question for application teams and architects that frequently make tradeoffs for cost benefits:

If carbon was the thing we’re optimizing for, would we make different choices?

Figure. Drew Engelson, Director of Engineering at Starbucks, discussing “TCO₂“

Get started, the sustainable way

At AWS, we encourage architects to build solutions with sustainability in mind. If your team wants to get started with the concepts from the AWS Well-Architected Sustainability Pillar, conduct a review of your workload in the Well-Architected Tool, or check out the AWS Well-Architected Framework and AWS Well-Architected Labs to learn more!