There was a time not long ago when we used relational databases for everything. Even if the data wasn’t particularly relational, we shoehorned it into relational tables, often because that was the only database we had. Thank god these dark times are over and now we have many different kinds of NoSQL databases: Document, realtime, graph, column, but that does not solve the problem that the same data might be a graph from one perspective, but a collection of documents from another. It would be really nice if we can access that same data in many different ways, depending on the context of what we want to achieve in our current task. As software architects this is not easy to solve but definitely possible: We can design an architecture using Event Sourcing: Capture the data with Debezium, post it to a Kafka queue, use Kafka Streams to model the data the way we like, and store the data in various different data sources, so we can synchronize data between data sources. But can we retrofit this on a more than a decade old application without downtime? Turns out you can. At Dexels we upgraded our 14-year old Sportlink application (based on Java and Oracle) to include MongoDb and Neo4j, to face our increasing user base. After a hectic summer and some long nights we can now easily use all the hipster data stores we like.
