Stop Building Fintech with Databases: Why I Went Local-First for Pocket Portfolio

Stop building fintech with databases. Why I went local-first for Pocket Portfolio.

For the last decade, building a fintech app meant one architecture: a centralized PostgreSQL database, a backend in Node or Python, and an API that hoards user data.

As an engineer, I always found this disturbing. Why does a portfolio tracker need my trade history stored on AWS us-east-1? It does not. It stores it because the data is the product, not the software.

I wanted to build a tool for modern investors — those of us using Trade Republic, Trading 212, or Robinhood — who want insights without surveillance.

So I set a hard constraint:

Zero user data leaves the client.

That constraint became the foundation of Pocket Portfolio — a privacy-absolute, local-first financial application.

Learn more about Sovereign Financial Tracking.

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The Zero-Server Stack

We stripped everything back.

There is no backend database.
No user accounts.
No cloud sync.

• The Core: Next.js (static export). The entire app is JavaScript shipped to the browser.
• The Database: Browser storage (localStorage and IndexedDB). Your financial data lives on your device, not ours.
• The Parser: Web Workers processing CSV files entirely client-side.

No servers storing user data.
No silent replication.
No surveillance by default.

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The Hardest Part: Client-Side Parsing

The hardest technical problem was not charts or performance.

It was standardizing messy, inconsistent CSV exports from more than 15 brokers — without sending a single byte to a server.

Each broker formats exports differently. Headers change. Dates vary by locale. Fees are embedded or omitted. Some files are technically valid CSVs but semantically broken.

So we built a robust, open-source parsing engine that runs entirely in the browser.

The flow looks like this:

1. User drops a CSV file (for example, a 5MB Trade Republic export).
2. The main thread hands the file to a Web Worker to avoid UI freezes.
3. The worker identifies the broker schema and normalizes each row into a standard JSON format.
4. Clean data is returned to the main thread and hydrated into application state.

All of this happens locally.
No uploads.
No APIs.

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The Market Has Spoken

I was not sure if other developers cared about this level of privacy. I was wrong.

Within the first seven days of soft-launching the parser engine on npm, it crossed 5,800+ weekly downloads.

Developers are already integrating the local parser into their own pipelines.

The takeaway is simple:

You do not need to hoard user data to build valuable software.

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Key Takeaways

Unlike cloud apps, Pocket Portfolio uses Sovereign Sync to turn your Google Drive into a database. This approach ensures:

• Data Ownership: Your financial data lives in your Google Drive, not a vendor's database
• No Vendor Lock-in: Export anytime, use any tool
• Privacy by Default: Your data never leaves your control
• Local-First Resilience: Works offline, syncs when online

Learn how to set up Google Drive Sync and turn your Drive into your personal financial database.

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Verdict

The fintech industry has normalized data hoarding. But you do not need a centralized database to build powerful financial software.

Pocket Portfolio proves that local-first architecture is not just viable — it is superior for user privacy and data sovereignty.

For more on Sovereign Financial Tracking, see our homepage.

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Try It (and Break It)

Pocket Portfolio is live.

If you are an investor or a developer tired of the current fintech status quo, try it with your messiest CSV file and see how the local engine handles it.

• Live App
• npm Package

We are also running a limited Founder's Club for early supporters who believe in local-first software and want lifetime access to advanced features.

Keep building.
Keep it local.

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🚀 Unlock Sovereign Sync

Ready to own your financial data?

Pocket Portfolio's Sovereign Sync turns your Google Drive into a personal database. No vendor lock-in. No cloud dependencies. Just your data, your way.

👉 Upgrade to Corporate/Founder Tier →

*Sovereign Sync is available for Corporate and Founder tier sponsors. Learn more → | Set up Google Drive Sync →