Here at KeyCore, we seek to give you latest updates in tech trends within AWS services, and Event Sourcing is no exception. In this two-parted blog-entry, we give you the benefits of Event Sourcing and demonstrate an event sourced system with a CQRS based API. We will use AWS Serverless services, such as API gateway, Lambda and DynamoDB to demonstrate how this can be done in a flexible, extensible manner, that requires a minimum of code.
In this last part we will look into querying the event store, and also demonstrate, how we could make use of S3, to store the newest snapshot of a projection over the events, which would make it possible to do analysis on the data, for instance via AWS Athena, or if the number of events per partition key is high, simply query S3 instead of DynamoDB, when we wanted the newest version. We will also demonstrate how we can travel back in time, and see how a projection looked at a given transaction time.