This is just a list of notes and facts I have gathered about Lagom. I’m the kind of person that asks 1 million questions and likes to know why things are done.
Why does Lagom use Cassandra as an event store system?
Lagom uses Cassandra as it’s event store. I wanted to know why they would choose Cassandra so I did some digging. I found the following video helpful in understanding why anyone would use Cassandra for an event store instead of EventStore itself. The video is not about Lagom, however it is about Cassandra and CQRS/Event Sourcing and why you would choose Cassandra as an event store. Basically Cassandra has features that are required for Event Sourcing and make it a good fit for it.
Why does Lagom use KAFKA as a Message Broker?
The documentation mentions using KAFKA as a Message Broker. I wanted to know why? This article helped clarify what the difference between a message bus and a message broker. Basically a broker gives a little less coupling with some other nice features. A message bus is more strict with a Schema like a traditional RDBMS database system, a message broker is more free like a NoSql database it has no Schema. Read the article for the other benefits and differences.
Codecentric: CQRS and Event Sourcing Applications with Cassandra
This video explains how to handle event sourcing with Cassandra
I also found this link to be helpful in understanding why Lagom would use Cassandra instead of EventStore. That article has a nice comparison of Cassandra vs other similar software used for event storage. A quick look at the features is all it takes.