Building Event-Driven Microservices

Chapter 4. Integrating Event-Driven Architectures with Existing Systems

Transitioning an organization to an event-driven architecture requires the integration of existing systems into the ecosystem. Your organization may have one or more monolithic relational database applications. Point-to-point connections between various implementations are likely to exist. Perhaps there are already event-like mechanisms for transferring bulk data between systems, such as regular syncing of database dumps via an intermediary file store location. In the case that you are building an event-driven microservice architecture from the ground up and have no legacy systems, great! You can skip this section (though perhaps you should consider that EDM may not be right for your new project). However, if you have existing legacy systems that need to be supported, read on.

In any business domain, there are entities and events that are commonly required across multiple subdomains. For example, an ecommerce retailer will need to supply product information, prices, stock, and images to various bounded contexts. Perhaps payments are collected by one system but need to be validated in another, with analytics on purchase patterns performed in a third system. Making this data available in a central location as the new single source of truth allows each system to consume it as it becomes available. Migrating to event-driven microservices requires making the necessary business domain data available in the event ...