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AI features that survive vendor changes.

Burraq Ur Rehman · Full-Stack Engineer, AI Voice and SaaS Product Lead

I design and ship full-stack SaaS products end to end, from the data model to the deployed interface: multi-tenant platforms and production AI features such as real-time voice agents, LLM tool calling, transcript pipelines and vector search.

View Case StudiesLet's Work Together
  • ClientsReact · Next.js · sockets
  • AuthAuth0 · JWT · tenant + role
  • APIFastAPI · NestJS · Rails
  • VoiceTwilio · Retell · Grok
  • JobsCelery → Stripe
  • LLMTool calls · pgvector
  • DataPostgreSQL · Redis
Fig. 1 How the products I build fit together. A composite across my projects. Connections: Clients to Auth, Auth to API, API to Voice, API to Jobs, API to LLM, Voice to Data, Jobs to Data, LLM to Data.
  • 5+ Years in Production
  • Real-Time AI Voice Agents
  • Multi-Tenant SaaS Platforms
  • LLM Tool Calling & Vector Search
  • 40% Faster Deployments
  • 35% Faster Response Times

Selected case studies

Problems solved in production

How I approach real backend problems: context, decisions, and trade-offs.

What I do

Full-Stack SaaS, From Data Model to Deployed Interface

My work covers the whole product: the data model, the API that decides who can see what, the background jobs that bill and notify, and the interface on top. AI features sit behind one abstraction, so a voice agent can move between Retell and x.AI Grok realtime with zero downtime, and billing runs are idempotent, so a retry never double-charges.

  • AI Voice Agents

    Inbound call automation with real-time tool calling for bookings, and transcripts saved to the CRM. Retell, x.AI Grok realtime, Twilio Media Streams and WebSockets.

  • LLM Features in Production

    Tool calling, retrieval-augmented generation and vector search inside real products, with validated, logged results. pgvector, embeddings and prompt design.

  • Multi-Tenant SaaS Products

    Platforms where the backend is the single authorization boundary for every role. FastAPI, NestJS, Rails, PostgreSQL, Auth0 and RBAC.

  • Billing & Payments

    Idempotent billing engines and subscription plans that never double-charge, on Stripe and background jobs (Celery, pg-boss).

  • Real-Time Platforms

    Live leaderboards, scoring and dashboards that stay in sync across processes, with Socket.IO, WebSockets and PostgreSQL LISTEN/NOTIFY.

  • Ruby on Rails Development

    New Rails products and feature work on existing Rails codebases, with access rules, RSpec coverage and reviewed releases. Devise, Sidekiq, RuboCop and Haml.

  • Legacy Rewrites & Hardening

    Audit, fix root causes, add tests that prove it, and ship through a CI-gated pipeline with pytest, Vitest, Playwright and GitHub Actions.

How I can help

Featured projects

Systems I've built

An AI voice platform for car dealerships, a multi-tenant tutoring LMS and CRM (confidential), and a live-scoring platform for pigeon racing.

Automotive / AI Voice SaaS

Otto Revenue Engine

Problem
Dealerships were losing revenue to missed inbound calls and dropped follow-ups.
What I built
An AI voice agent that answers inbound calls, books appointments through real-time tool calling and persists transcripts, on two voice providers behind one switchable abstraction.
My role
Built the multi-tenant platform, Voice pipeline and telephony webhooks, Real-time tool calling for bookings, Provider-agnostic voice abstraction
  • Python
  • FastAPI
  • PostgreSQL
  • Celery
  • React 18
  • TypeScript
Project details Read case study

EdTech / SaaS (LMS and CRM)

Multi-Tenant Online Tutoring Platform

Problem
The academy needed leads, scheduling, classes, attendance, billing and tutor payouts in one system, across four role classes.
What I built
A multi-tenant platform with the backend as the sole authorization boundary, a 373-endpoint API, 176 migrations and an idempotent Stripe billing engine.
My role
Architected and shipped it end to end, Idempotent Stripe billing engine, Expand, migrate, contract migration policy, Pre-deploy quality gates
  • Next.js 16
  • React 19
  • FastAPI
  • Python 3.14
  • PostgreSQL
  • pgvector
Project details Read case study

Sports / Real-Time Platform

Pigeon Premier League

Problem
The legacy system carried 17 documented correctness and security defects.
What I built
A full rewrite with live leaderboards, race-day time capture and a permission-scoped admin panel, on a three-process architecture over PostgreSQL alone.
My role
Built and deployed the rewrite, Three-process architecture, Cross-process live updates, Tests and CI/CD pipeline
  • TypeScript
  • NestJS 11
  • Prisma 6
  • PostgreSQL
  • React 18
  • Socket.IO
Project details Read case study
All projects

Technical expertise

The stack I work in

Languages
Ruby, Python, TypeScript, JavaScript, SQL, HTML5, CSS3
Frameworks
Ruby on Rails, FastAPI, NestJS, Next.js, Node.js, Express.js, Django, Flask, Celery, Pydantic v2, SQLModel
Frontend
React 18 & 19, Angular, Vite, TanStack Query, Redux, Context API, Tailwind CSS, shadcn/ui, Bootstrap, jQuery, AJAX
Backend
REST APIs, Microservices, Multi-Tenant Architecture, WebSockets, Socket.IO, Sidekiq, pg-boss, RBAC, JWT & JWKS Auth, Auth0, Devise, Passport, Stripe Billing, Third-Party Integrations
Databases
PostgreSQL, pgvector, SQLAlchemy 2 (async), Prisma, Alembic, Redis, NoSQL, Query & Schema Optimization
AI & ML
LLM Integration, Tool Calling, Real-Time Voice Agents, Retell, x.AI Grok Realtime, Twilio Media Streams, Transcript Processing, Embeddings & Vector Search, RAG, Prompt Design, scikit-learn Basics
Cloud & DevOps
AWS (EC2, S3, Lambda, RDS, CloudWatch), Vercel, Railway, Heroku, Docker, GitHub Actions, CI/CD, Nginx, PM2, Linux
Testing & Quality
pytest, RSpec, Playwright, Vitest, ruff, mypy, ESLint, RuboCop, Code Review
Ways of Working
Agile & Scrum (Scrum Master), Jira, Git, GitHub, GitLab, Bitbucket, Client Communication

Experience

Professional experience

  1. Full-Stack Developer · Xprolabs

    Oct 2021 — Present

    • Shipped and maintained in-house modules end to end with TypeScript, React, Ruby on Rails and Node.js
    • Built CI/CD pipelines with automated testing that cut deployment time by 40%
    • Optimized complex SQL queries and backend architecture, improving response times by 35% (Performance Excellence Award, 2023)
    • Led the 2023 launch of a computerized maintenance management system (CMMS), improving operational efficiency by 45%
    • Designed RESTful APIs in Node.js powering React front ends across several product surfaces, and built internal tooling that improved developer productivity
    • Worked with solution architects, UX designers and systems analysts on cross-brand modules for the Traton group (MAN and Navistar), led multilingual support features, and customized the core product to client requirements
    • Mentored 3 junior developers on coding standards and code review, with 100% retention

  2. Associate Software Engineer · Southville Solutions

    Mar 2021 — Oct 2021

    • Delivered features across Node.js, JavaScript, TypeScript, React and Angular in agile sprints
    • Built responsive UIs with HTML5, CSS3 and Bootstrap, and developed task management and web scraping solutions
    • Became a productive contributor within the first sprint cycles

How I work

Engineering principles

  1. The backend is the boundary

    Every request resolves its tenant and role on the server before a scoped query runs, so a tenant only ever sees its own data.

  2. Providers behind one switch

    Voice and LLM providers sit behind one abstraction, so changing vendors doesn't mean a rewrite or downtime.

  3. Money paths are idempotent

    Billing runs carry an idempotency key, so a retried run produces one invoice, never two.

  4. Root cause, tests, gated deploy

    Audit, fix the root cause, add tests that prove it, and ship through a CI-gated pipeline.

Building a SaaS product with AI in it?

From the data model to the deployed interface: multi-tenant platforms, AI voice agents, LLM features and Stripe billing.

Let's Work TogetherView Case Studies
Work with Carpediemsoft

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Have a Product to Build?

Building a SaaS product, adding AI voice or LLM features, or rescuing a legacy codebase? Tell me what you're working on.