Event Sourced Loyalty Program

POC for a loyalty program with event sourcing in Go.

Business Logic

• Users get 100 points for signing up without a referral
• Users get 200 points for referring a user
• Users get 200 points for signing up with a referral code
• Users get 50 points for creating their profile

Events

Wallet Aggregate

• PointsEarned

User Aggregate

• UserCreated
• UserDeleted
• ReferralCreated
• ReferralCompleted

TODO

• Add Flow chart illustrating data flow
• Add fx modules
• Snapshots
• Pause and Restart projectors
• Enforce ordering in the read model. Maybe locks updates for a particular aggregateID until processing finishes
• Event handlers load events into memory, apply the new events on the read model aggregate, then save changes to ensure business logic
• PointsRedeemed
• How to ensure unique values with eventual consistency (unique username for CreateUser). Maybe the approach is to have a immediately consistent data store that houses all of the usernames in the system. Then, check that datastore and update it before accepting the command to CreateUser. A better approach may be handling the remediation through events. Still check the read model before submitting a command, but if a duplicate username makes it's way to the read model, update the username and send an email the user letting them know that their username was already taken and that we've assigned them a new one.

Ideas

type ProjectorStatus string

const (
	ProjectorStatusStopped = "Stopped"
	ProjectorStatusPaused  = "Active"
)

type Projector interface {
	Status() ProjectorStatus
	Start() error
	Stop() error
}