Tableau-experienced only - Advanced In-Browser BI Report Builder

BI Report Builder — React/FastAPI (Tableau-experienced only)

We're building a visual, drag-and-drop report builder inside our enterprise HRMS SaaS — think simplified Tableau embedded in a web app. If you've only done basic dashboards, this isn't the role.

What we're building:
A canvas where users drag data entities (employees, invoices, timesheets, etc.), connect them visually, pick columns, configure chart types, and generate cross-entity reports — all in-browser without SQL knowledge.

What's already done:

Backend already supports multi-source SQL JOINs with full injection protection and tenant isolation
22 pre-aggregated data entities with 17 predefined valid join relationships
Chart rendering components already built (bar, line, pie, area, funnel)
We need the visual builder layer on top
What you'll build:

Drag-and-drop canvas (ReactFlow) with entity nodes showing selectable columns
Auto-detect valid joins between placed entities, let users configure join types
Right panel: configure dimensions, measures (aggregation/format), filters, sort, chart axes
Preview and save reports, integrate with existing chart rendering
Stack: React 19, Next.js 15, FastAPI async (Python), PostgreSQL, MUI v7, Zustand, ReactFlow

You must have:

Built production BI/analytics UIs — not just consumed them. Show us something.
Worked with Tableau, Power BI, or Metabase (as a developer, not just a user)
Full-stack capability (Python FastAPI backend + React frontend)
What we don't want: Someone who'll Google "how to build a dashboard" for the first time on our project.

Scope: 1 week. Fixed price preferred. Share relevant portfolio — no work, no interview.