Architecture Principles

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Postel's Law

Postel’s Law, also known as the robustness principle states that you should be conservative in what you send and liberal in what you accept from others. Although this was proposed initially for the specification of the TCP protocol, it has a very important place in the design and evolution of service interfaces. It is difficult to accurately anticipate how requirements are going to change or how many different types of consumers a service will support. Ensuring that services are lenient and robust (e.g. by ignoring additional information in requests that they don't understand) decouples those services from their consumers. This is fundamental in a micro-service environment where the dependencies between services should be kept to a minimum, especially when considering releases.