Legacy Systems and Distributed Monoliths
We can't have all the software in one system, even if we try. By nature, distribution will always happen. Decades ago, SOA set the standard for creating proper services that prime interoperability. Distribution is not bad; it's how systems work at scale. When companies buy products, they add more distribution because there is no system in a complete vacuum. Now, when we have distribution instead of modules in a monolith, we need to have a way for the system to communicate. When we have a proprietary system, communication options can often be pretty limited. Ideally, communication is thought ahead of time in an approach we call contract first. Where we define contracts and explicitly manage contracts aiming for interoperability. Usually done via a common interoperable interface like HTTP or, nowadays HTTP/2 or even HTTP/3. Legacy systems usually are not API friendly and, therefore, limit your ways of comunication. Such limitations can be drastic to the point where you might only