Personal Budget Tracker API

Overview

The open-source ASP.NET Core engine behind Nqood: a privacy-first REST API that combines SQL Server, Redis, and MongoDB in a dual-layer snapshot architecture, enforcing financial rules and surfacing patterns through a pre-aggregated statistics engine.

Architecture

SQL Server is the source of truth; Redis holds live daily totals; MongoDB stores completed-day documents. Hangfire drives scheduled transactions. The statistics engine reads only pre-aggregated data.

Tech stack

Key features

• Two-layer snapshot architecture (SQL Server → Redis → MongoDB)
• Configurable financial rules engine with a cached confirm/cancel flow
• Scheduled recurring transactions via Hangfire background jobs
• Statistics engine: dashboards, top categories, income/expense ratios, period-over-period change
• 40+ REST endpoints across 9 controllers with filtering and pagination
• Global soft-delete and an automatic audit trail

Engineering highlights

• Atomic Redis HINCRBYFLOAT updates for O(1) per-transaction write cost
• TPH inheritance for transaction and rule types via EF Core discriminators

Outcome

• Published as open source and powering the Nqood app