Functional Event-Sourcing in Kotlin

A toy project to explore the capabilities of functional event-sourcing using Kotlin

User Stories

The project try to implement the following user stories. The domain is a simplified stock trading system.

• A user should create a new portfolio.
• A user should buy stocks for an existing portfolio.
• A user should sell stocks that it owns.
• A user should close a portfolio.

Event Storming / Domain Modeling

The following diagram shows the domain model of the system. The model is based on the user stories above.

Technology Stack

The project uses the following technologies:

• Kotlin
• Arrow Kt
• Ktor
• Kotlinx Coroutines Flow
• EventStoreDB
• SQLDelight
• Kotest
• Testcontainers
• Mockk
• Ktlint

References

The project is heavily inspired by the following resources:

• Functional Event Sourcing Decider by Jeremie Chassaing
• Event sourcing Series' Articles by Jakub Zalas
• Ktor Arrow Real World Example by Simon Vergauwen