In the final part of a series on APIs, sustainability, and climate change, the text explores the environmental impact of common architectural trends and provides recommendations to mitigate it. The shift from monolithic systems to microservices is highlighted as a popular transformation that improves resource efficiency, yet increases network traffic, which can be managed through appropriate protocols like gRPC and service mesh technologies. The text advocates for event-driven architectures (EDA) over synchronous RESTful APIs to reduce wasted energy from idle API polls, promoting the use of pub/sub patterns for asynchronous processing. Additionally, it argues for an API-first integration approach to minimize idle resource consumption compared to point-to-point integrations, emphasizing the importance of managing APIs through a gateway for auditing and optimization. The author calls for the acknowledgment of IT's role in global energy consumption and urges readers to adopt green engineering principles in their technology practices to combat climate change.