Every application proposal trying to win the heart of a Fortune 500 company today not only needs to claim to be Agile—oh, sorry, SAFe—but also based on a microservices architecture. After high-profile microservices disasters like Dell’s, we understand that a myopic microservices approach may not end up well. What if we could have all the benefits of a microservices architecture but none of the drawbacks?

Why, sometimes, you should just stick to boxes.

The T-shirt size model is convenient for pricing software but it may cause problems if used incorrectly.

In this article we explore the Event Sourcing Pattern and its cousins (Retroactive Event, Parallel Models and Materialised View) using a Haskell model to investigate the implications of implementing said patterns and the challenges that arise from their use. In particular, we note that the Retroactive Pattern is difficult to implement in an efficient manner whenever the possibility of inserting an arbitrary number of “missed” events between existing events is desirable.

The Command and Query Responsibility Segregation (CQRS) Pattern is a solution to the problems that are inherent to the Create, Read, Update and Delete (CRUD) approach to data handling. We use Haskell to explore the problem scope and the proposed solution described by the pattern.