When building enterprise FinTech tools, the standard industry playbook usually looks like this: build a React/Vue frontend, send sensitive user financial data via REST API to a heavy backend (like Python/FastAPI or Node.js), crunch the numbers, and send the result back.
But when we built the SEOSiri CapEx Engine (https://capex.seosiri.com) for multinational capital budgeting, we realized this standard API-driven architecture had a massive flaw: Data Privacy & Sovereignty.
To convince CFOs to test complex global capital allocations, we couldn't ask them to transmit highly sensitive financial strategies to an external server. So, we threw out the backend API entirely.
Here is how we built a "Sovereign, Browser-Based" financial engine.
The Architecture: 100% Client-Side Execution
