Freelance Web Developer — Wrap an Existing Python Engine into a SaaS Web App

# Freelance Web Developer — Wrap an Existing Python Engine into a SaaS Web App ## Short version (for the listing headline / summary box) We have a **working, tested Python engine** that reviews architectural PDF drawings and flags QA/code issues. We need a full-stack developer to wrap it in a production web app: user accounts, PDF upload, background processing, a results viewer with PDF markups, subscription billing (Stripe), and cloud deployment. **The hard analysis engine is already built — this is integration and product build, not R&D.** --- ## About the project We are building a SaaS tool for architecture firms that automatically reviews drawing sets for quality-control and building-code issues, then returns a redlined PDF and an issue report. The core review engine (Python) is complete and verified, including a working FastAPI prototype with a basic upload page. Your job is to turn that prototype into a polished, secure, multi-tenant commercial product that firms can sign up for and pay to use. You will be given: the full engine source code, a FastAPI starter app, a deployment architecture document, and an API spec. The engineering decisions are already documented — we need a strong builder to execute them. --- ## Scope of work 1. **Backend / API (Python, FastAPI)** - Build on the existing FastAPI prototype. - Replace the in-memory job store with **PostgreSQL** (users, organizations, projects, jobs, findings — all scoped per organization / multi-tenant). - Replace background threads with a real **job queue + worker** (Celery + Redis, or an equivalent) so large PDF reviews run asynchronously. - File handling via **S3-compatible object storage** (uploads + generated marked-up PDFs), encrypted, with signed download URLs. 2. **Authentication & multi-tenancy** - User sign-up / login and organization accounts (use a hosted provider such as Auth0 / Clerk / Supabase Auth — not hand-rolled auth). - Strict data isolation: every query scoped to the user's organization. 3. **Frontend (React)** - Clean, responsive UI: project setup form, drag-and-drop PDF upload, job progress, and a **results view that displays the drawing with the markups** using a PDF viewer (e.g. PDF.js). Issue list with severity filters; download buttons for the redlined PDF and report. - We will provide a basic HTML prototype of the results screen to match. 4. **Subscription billing (Stripe)** - Free tier and paid tier(s). A **server-side feature gate** (already designed in our code) must enable/disable premium features based on the org's plan. - Stripe Checkout + Customer Portal; webhook that updates the org's plan in our database on subscribe / cancel / payment failure. Usage metering for plan quotas. 5. **Deployment & DevOps** - Containerize (Dockerfile exists) and deploy to a cloud host (Render / Railway / Fly.io / AWS — your recommendation welcome). - Managed Postgres, object storage, environment-based secrets, basic logging and error monitoring (e.g. Sentry). A simple CI deploy pipeline. 6. **Handover** - Clean, documented code in our Git repo; a short runbook for deploy/config; a walkthrough call. **Out of scope:** the drawing-analysis logic itself, and any machine-learning model training. You are integrating our engine, not modifying how it reviews drawings. (A separate future phase covers ML; not part of this contract.) --- ## Required skills & qualifications - **3+ years full-stack web development**, with shipped production SaaS apps. - **Strong Python + FastAPI** (or very strong Flask/Django willing to work in FastAPI). You must be comfortable reading and integrating an existing Python codebase. - **React** (or Next.js) for the frontend; comfortable with REST APIs and async job/polling patterns. - **PostgreSQL** schema design; multi-tenant data isolation. - **Background job processing** (Celery/Redis, RQ, or cloud queue). - **Cloud object storage** (AWS S3 or compatible) and **Docker**. - **Stripe** subscription integration, including webhooks and customer portal. - **Authentication** integration (Auth0 / Clerk / Supabase or similar). - Security fundamentals: tenant isolation, encryption in transit/at rest, secrets management, handling confidential client files. - Clear written English and Git-based collaboration. ## Nice to have (not required) - Experience with **PDF handling** (PyMuPDF / pdf.js) or document-processing apps. - Prior work on **AEC / construction / architecture** software. - Experience integrating **LLM/AI APIs** (Anthropic / OpenAI) — our engine already has an AI module; you'd just wire its API key + the billing gate. - DevOps / infrastructure-as-code (Terraform), CI/CD. --- ## What we provide - Complete, working Python review engine (well-structured, documented). - A FastAPI prototype that already does upload → review → marked-up PDF + report. - Deployment architecture doc, API endpoint spec, and a results-screen UI mockup. - Sample PDF test files and expected outputs for verification. ## Deliverables & acceptance - A deployed, working web app where a firm can sign up, upload a PDF, pay for a plan, and receive a redlined PDF + issue report. - Multi-tenant, secure, with the subscription gate enforced server-side. - Source in our repository + deploy runbook + handover call. - Acceptance = the full sign-up → pay → upload → result flow works end-to-end on the live deployment using our sample files, with data isolation verified. ## Engagement details (edit before posting) - **Type:** Fixed-price milestone project (recommended) or hourly. - **Suggested milestones:** (1) backend + DB + queue + storage, (2) auth + frontend results viewer, (3) Stripe billing + gate, (4) deploy + handover. - **Budget:** [your range] · **Timeline:** [your target, e.g. 6–10 weeks] · **Time zone overlap:** [your preference]. - **To apply, please include:** (a) 2–3 live SaaS apps you've shipped (links), (b) one that used background job processing or file uploads, (c) your approach to multi-tenant data isolation, (d) rough estimate + timeline. Applications without portfolio links will not be considered. ## Confidentiality This involves proprietary software and confidential architectural drawings. Shortlisted candidates must sign an NDA before receiving the codebase. Please do not republish or reuse any materials provided.