How I Built a Serverless AI Accounting App with AI assistant and Saved My Family from Spreadsheet Chaos

Link to the Source Code As a data engineer, I spend my days designing clean, optimized data structures. But at home, I face a much tougher crowd: my family. We manage our shared finances together to optimize our budget, and because of where we live and work, we have to do this in several different currencies (like USD, EUR, CZK, and UAH) Like any developer, I first tried to find a ready-made app to solve this. But I ran into a classic problem: they were either bloated with a million features we didn’t care about, or they were missing the exact features we actually needed. So, we did what any desperate family does: we opened a Google Sheet . We tracked our money there for a while, not because it was perfect, but because it helped us figure out what we actually needed from a real application. It was our "living schema design" before I wrote a single line of code. In this article, I want to show you how I looked at this problem from two sides—as a frustrated user who just wants to log expenses, and as a data engineer obsessed with clean database design. Here is the story of how I built our custom home accounting server. Part 1: Django, a Star Schema, and the Framework Battle By 2025, I was ready to replace our Google Sheet. My main programming language is Python, so I had three realistic choices: FastAPI, Flask, or Django. FastAPI is the cool kid on the block for high-speed APIs, but we didn’t expect millions of requests (unless my family suddenly grew by a factor of a million). We also needed a friendly web UI, which FastAPI isn't naturally built for. I had just used Flask for my previous project, but I wanted to challenge myself and learn something new. Django felt like an old friend I hadn't seen in years. It has amazing built-in tools (like the admin panel and great translation support), and using it was the perfect way to refresh my skills and grow as a developer. The Database: Why a "Star Schema" Actually Makes Sense As a data engineer, I didn’t want a messy data