Full Stack Developer — Custom ERP System (PostgreSQL / FastAPI / React)

We are a British/Irish food distribution company based in the US building a custom ERP system to replace QuickBooks Enterprise Desktop. The system is purpose-built for our business and handles the full order-to-cash and purchase-to-pay cycle, including multi-currency financials, lot code tracked inventory, Zebra WiFi scanner integration, AI phone ordering, and a customer self-service portal.

The core application code is AI-assisted and well-structured. We are looking for a developer to deploy the system, set up the infrastructure, test thoroughly, fix bugs, and maintain it ongoing. You will not be starting from scratch — you will be building on a solid foundation.

TECH STACK

• Database: PostgreSQL 15+

• Backend: Python 3.11 + FastAPI

• Frontend: React 18 + TypeScript

• Hosting: AWS or Azure (you recommend)

• Email: SendGrid API

• Voice AI: Twilio + OpenAI Whisper + GPT-4

• EDI: X12 and EDIFACT

• Label printing: ZPL over WiFi to Zebra printers

• Scanner integration: Zebra Android handhelds via browser

KEY FEATURES YOU WILL DEPLOY AND MAINTAIN

• Multi-currency invoicing and AR (USD, GBP, EUR) with live exchange rates

• Lot code and expiry date tracking with FIFO picking and recall reporting

• Full AP/bills module with three-way PO matching

• Zebra WiFi scanner workflows: receiving, pick/ship, stock counts, lot checks, label printing

• AI phone ordering: customer calls in, AI takes order verbally, enters into system

• Gap Sell button: surfaces top sellers a customer doesn't currently order

• Customer self-service portal: view invoices, statements, order history

• EDI integration: inbound orders, outbound invoices and ASNs (X12 / EDIFACT)

• Email invoices via SendGrid with delivery tracking

• User roles: Admin, Sales, Warehouse

• Full report suite: P&L, Balance Sheet, AR/AP Aging, Inventory Valuation, Lot Trace

YOUR ROLE

• Set up cloud hosting environment (AWS or Azure)

• Deploy PostgreSQL database and FastAPI backend

• Configure all third-party integrations (SendGrid, Twilio, OpenAI, exchange rate API)

• Conduct thorough testing of all modules

• Fix bugs and edge cases identified during testing and live use

• Provide ongoing maintenance and support after launch

• Support data migration from QuickBooks Desktop (CSV/IIF export)

• System will run parallel with QuickBooks during transition period before full cutover

WHAT WE ARE LOOKING FOR

• Proven experience with PostgreSQL, Python FastAPI, and React — all three are essential

• Demonstrated experience deploying financial, inventory, or ERP-type applications

• Comfortable working with AI-generated codebases — you are maintaining and improving, not architecting from scratch

• Experience setting up cloud infrastructure on AWS or Azure

• Familiarity with Twilio and/or OpenAI API integration is a strong advantage

• EDI experience (X12 or EDIFACT) is a strong advantage

• Strong English communication — we will have regular calls to discuss progress

WHAT WE ARE NOT LOOKING FOR

• Developers who want to rebuild the stack from scratch

• Agencies — we want one dedicated developer we can build a long-term relationship with

• Developers without demonstrable financial or inventory application experience

ENGAGEMENT

We are open to either a fixed-price quote per phase or an hourly arrangement with clear milestones. Please indicate your preference and provide an estimate in your proposal. We expect this to be a long-term relationship — we are not looking for someone to hand off after launch.

TO APPLY

Please include in your proposal:

1. Examples of financial, inventory, or ERP systems you have built or deployed

2. Your experience with each technology in our stack

3. How you would approach setting up the hosting infrastructure

4. Your availability and estimated timeline for Phase 1 (core ERP deployment)

5. Your hourly rate or fixed-price estimate

Proposals without relevant portfolio examples will not be considered.

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