PostgreSQL on Artur Rios Lab

Netbank: A Banking System to Learn From

Thu, 22 Oct 2026 12:30:00 +0000

A complete banking system, built for learning purposes.

Technology

.NET on the back end
Flutter on the front end
Heimdall for authentication and authorization
PostgreSQL database

Platforms

Android
Linux
Windows
Web

What a complete bank covers

“Complete” is the part of the idea that needs a boundary. A real bank is hundreds of systems, so this is a suggestion of what Netbank should cover, chosen because each part teaches something a CRUD app does not. It moves no real money and connects to no real bank: every institution outside Netbank is simulated.

Sizing the Server

Wed, 21 Oct 2026 17:55:00 +0000

Before an application goes on the server, it should be clear that it fits. This is the model I size the server with: one figure per service for what it needs, a formula that adds headroom, and the signals that say the model has stopped being true.

The figures are starting estimates for a small production load, a few requests a second on each API, not measurements. After a week of real traffic, Grafana’s numbers replace them.

The Server

Wed, 21 Oct 2026 17:55:00 +0000

Everything self-hosted runs on one machine: the platform, the deploy server, and every application in three environments. This part covers the machine itself and what is installed on it directly, outside any container.

The machine

Resource	Spec
Provider	Hostinger VPS
vCPU	4 cores
RAM	16 GB
Disk	200 GB NVMe
Bandwidth	16 TB a month
OS	Ubuntu LTS

One machine is a single point of failure, and I accept that knowingly: these are my own projects, an outage costs me an evening, and one well-understood server is easier to keep healthy than three. Whether everything fits on it is the subject of Sizing the Server.

Web APIs

Wed, 21 Oct 2026 17:55:00 +0000

My backends are ASP.NET Core APIs, and every one of them meets the platform the same way. Heimdall’s API is the example throughout; Fortuna’s follows the same shape.

Concern	Choice
Framework	ASP.NET Core on .NET 10
Image	Multi-stage: the SDK to build, the ASP.NET runtime to run
Database	The host’s PostgreSQL, one database per environment
Configuration	Environment variables, from yggdrasil
Health	`/healthcheck`, probed by Docker, yggdrasil and the status API
Metrics	OpenTelemetry’s Prometheus exporter, on port 9464
Logs	Standard output, shipped to Loki
Checks	Tests and a Docker build in GitHub Actions

The image

The Dockerfile has two stages. The first restores and publishes with the .NET 10 SDK, copying the project files before the sources so a source-only change reuses the cached restore. The second copies the output onto the much smaller ASP.NET runtime image, and runs it as the image’s own non-root user: