WiSave Expenses Microservice

Event-sourced expenses backend with DDD, CQRS, and MassTransit.

Architecture

• KurrentDB — event store (source of truth)
• PostgreSQL — config/reference data + read model projections
• RabbitMQ/MassTransit — async command transport and committed-event distribution

Executables

Service	Description	Port
WebApi	REST API — publishes commands, queries projections	5200
Worker.Domain	Consumes commands, executes domain logic, appends events, forwards committed KurrentDB events to RabbitMQ	—
Worker.Projections	Consumes RabbitMQ committed events and builds read models in Postgres	—

Class Libraries

Library	Responsibility
Contracts	Shared commands, integration events, models (NuGet package)
Core.Domain	Aggregates, domain events, value objects (zero dependencies)
Core.Application	Command handlers, repository abstractions
Core.Infrastructure	KurrentDB, Postgres, MassTransit implementations
Projections	Read models, projectors, query handlers

Runtime Flow

1. WebApi publishes commands to RabbitMQ.
2. Worker.Domain consumes commands and appends domain events to KurrentDB.
3. Worker.Domain forwarder reads committed events from a Kurrent persistent subscription and republishes them to RabbitMQ. The subscription group is configured for a single active subscriber using DispatchToSingle.
4. Worker.Projections consumes committed events from RabbitMQ and updates Postgres read models.
5. WebApi reads projections from Postgres.

Local Development

# Build
dotnet build WiSave.Expenses.slnx

# Run tests
dotnet test WiSave.Expenses.slnx

# Run with Docker
docker compose up --build

Ports

Service	Port
Expenses WebApi	5200
KurrentDB UI	2113
PostgreSQL	5433

RabbitMQ is hosted by Portal (localhost:5672).

Contracts Package Versioning

WiSave.Expenses.Contracts uses Nerdbank.GitVersioning for package versions.

• Pull requests targeting master publish preview packages to GitHub Packages.
• Pushes to master publish stable packages to the same feed.
• The package version is not hardcoded in the contracts .csproj; it is derived from git history and version.json.

The current contracts version line starts at 1.0.

Design Docs

• Microservice Design Spec
• Implementation Plan
• API Contract ADR