Andy Nkumane | Backend Software Engineer

Selected work

From problem to working project.

Explore database-backed applications, a C# location API, Python tools, and data analysis. Start with the case studies for a closer look at implementation decisions and tradeoffs.

Buddy Budget landing page with a sample monthly budget preview — Featured project · Database-backed application

Buddy Budget

React
TypeScript
Supabase
PostgreSQL

A monthly budgeting application that turns recurring income and expenses into independent monthly snapshots.

**Design goal:** Let the plan change without rewriting past budgets. Snapshot fields preserve each month's names and amounts when a template changes.

Visit Buddy Budget View source on GitHub

Engineering decisions and tests

Preserve the history

Monthly records copy template values instead of reading a changing plan. A database function creates the month and its items in one transaction; a unique user/month constraint prevents duplicate months.

Inspect the schema and snapshot function

Enforce rules in the database

PostgreSQL row-level policies restrict records to their owner. Authenticated users cannot edit months two or more calendar months old; database triggers enforce the cutoff using the profile's timezone.

Inspect the historical-month rules

Test the failure cases

pgTAP tests cover cross-user access, snapshot preservation, and historical locks. Vitest tests cover money, validation, and UI state. The repository also includes an opt-in Playwright flow for a dedicated test account.

Inspect the database tests

Tradeoff: A static React frontend uses Supabase Auth and database APIs, with no custom application server. This keeps hosting simple but retains browser-managed sessions. Offline financial editing is outside the current scope.

Illustration of delivery vans on a street map with lime location pins — ASP.NET Core API · Prototype

Fleet Management System

C#
ASP.NET Core
Entity Framework Core
SQLite
Leaflet

A vehicle-location prototype pairing a C# HTTP API with a browser map. The API reads and updates vehicle coordinates; the dashboard polls every 30 seconds and generates simulated movement.

**Engineering focus:** Validate incoming coordinates, persist one location record per vehicle with EF Core, and display the stored positions in a table and map.
View Fleet Management System source

API implementation and prototype limits

Read and update locations

The locations GET endpoint returns vehicle IDs, coordinates, and timestamps. The location POST endpoint rejects missing IDs and out-of-range coordinates, then inserts or updates a vehicle record and returns HTTP 204.

Inspect the location API

Connect storage to the map

ASP.NET Core injects an EF Core database context into the controller. Development uses SQLite. Leaflet displays the coordinates returned by the API; a client-side loop posts random offsets to simulate movement.

Inspect the polling and simulation

Define the next iteration

This is a local prototype, not a live GPS service. The next steps are endpoint authentication, safe rendering of vehicle IDs, configurable API URLs, and tests aligned with the actual HTTP responses.

Inspect the current test code