The concept of upstream and downstream in microservices can be confusing, but understanding it is crucial for long-term success. APIs are interconnected systems that rely on other components to function, forming a flow often referred to as a stream. In this context, upstream systems provide raw data, while downstream systems consume the processed output. Dependencies complicate the upstream/downstream relationship and must be understood in order to make informed decisions, contributing to long-term success and user satisfaction. The complexity of dependencies increases with inherited dependencies, creating a chain that extends further downstream as systems evolve. A clear grasp of upstream and downstream dynamics is vital for the health of the industry and the success of any API implementation.