Building Event-Driven Microservices, 2nd Edition

Chapter 6. Integrating Event-Driven Architectures with Existing Systems

Transitioning an organization to an event-driven architecture requires the integration of existing systems. 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. This chapter covers how you can start making important business data available through event streams instead.

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 broker, consumable as event streams. Doing so is a process known as data liberation, and involves sourcing the data from the existing systems and state stores that contain it.

Data produced to an event stream can be accessed by any ...