Skip to content

Available for freelance & contract work

Senior Full-Stack Developer & AI Engineer

I build production-grade web applications, AI-powered systems, and scalable backends for startups and growing businesses. 5+ years shipping real products across SaaS, fintech, healthcare, and AI.

Start a projectView selected workGitHub
Years shipping production software
5+Years shipping production software
Job Success Score on Upwork
100%Job Success Score on Upwork
Contracts delivered
13+Contracts delivered
Hours billed
1,400+Hours billed

01Selected Work

Products in production, not prototypes.

Seven builds across SaaS, AI, fintech, and consumer mobile. Each one links to a short case study covering what it does and how it's built.

SaaS Platform

E-Arbitrator

AI-powered dispute resolution SaaS connecting arbitrators with clients, on Spring Boot microservices.

  • Spring Boot
  • React
  • PostgreSQL
  • Stripe
  • Zoom
  • +4
Read case study
AI Platform

The Holistic Researcher

A RAG system that aggregates and normalizes multi-source data into grounded, explainable AI output.

  • RAG
  • Claude API
  • OpenAI
  • pgvector
  • Node.js
  • +2
Read case study
AI Voice Platform

VoiceOS

Production AI voice agents for call centers, clinics, real estate, and law firms — sub-600ms latency.

  • Retell AI
  • Voice AI
  • Node.js
  • Supabase
  • Twilio
  • +3
Read case study
Marketplace App

Bayut Pro

Large-scale real estate marketplace with Mapbox clustering and viewport queries at high traffic.

  • React Native
  • Mapbox
  • Node.js
  • PostgreSQL
  • iOS
  • +1
Read case study
Consumer Mobile App

Mad Muscles

High-traffic fitness app with personalized plans, Stripe subscriptions, and analytics at scale.

  • React Native
  • Stripe
  • Firebase
  • Node.js
  • iOS
  • +1
Read case study
Fintech App

RasandPay

Fintech mobile app with secure transaction flows, card management, and ACH/wire support.

  • React Native
  • Node.js
  • PostgreSQL
  • AWS
  • Fintech
Read case study
Fintech BackendConfidential

Fintech Transaction Platform

ACH and wire transaction backends supporting pacs.008, camt.053, and camt.056 banking standards.

  • Java Spring Boot
  • NestJS
  • PostgreSQL
  • AWS
  • SFTP
  • +1
Read case study

02Experience

Where I've done the work.

  1. Jul 2025 — Present

    SobrietyHub

    Senior Platform Engineer

    Remote

    • Ship features across a multi-service SaaS platform for sober living homes — a React Native resident app, a Next.js admin web app, and AWS-hosted microservices
    • Designed and built "Phases", a stage-based resident progression system: four new domain entities with interval-based history for progression analytics and audit, plus per-phase curfew, visitor-policy, and requirement configuration
    • Delivered a HIPAA Safe Harbor-compliant de-identification pipeline for account cancellation, nulling and generalizing PII and sub-state geographic identifiers while preserving row structure for aggregate analytics
    • Rebuilt CI/CD on GitHub Actions with OIDC keyless auth, branch-to-environment routing across three AWS accounts, per-developer deployments to isolated ECS services, and fail-closed guards against misrouted deploys
    • Stood up a greenfield AWS dev environment in Terraform mirroring staging: VPC and subnets, RDS, S3, API Gateway, four ECS Fargate services, and a Lambda WebSocket authorizer — cutting dev cost with Fargate Spot and enabling deployment circuit breakers with auto-rollback
    • Built an automated chore rotation algorithm with offset-based fair distribution that survives mid-cycle roster changes, scheduled via Vercel cron
    • Built a resident self-service portal with an edit-request approval workflow, feature-flagging infrastructure across three repos for staged rollouts, and Stripe ACH microdeposit verification
    • TypeScript
    • React Native (Expo)
    • Next.js
    • Node.js
    • Prisma
    • PostgreSQL
    • AWS
    • Terraform
    • GitHub Actions
    • Stripe

  2. Jun 2024 — Present

    AshSol

    Backend Engineer

    Islamabad, Pakistan

    • Designed and implemented scalable microservices for a fintech platform processing real-time ACH and wire transactions
    • Built secure SFTP-based file processing pipelines for banking integrations, replacing manual workflows and improving efficiency by 80%
    • Developed event-driven and queue-based systems for time-sensitive financial operations with fault tolerance
    • Implemented KYC and compliance workflows using Spring Security
    • Java
    • Spring Boot
    • NestJS
    • TypeScript

  3. Apr 2022 — May 2024

    ZIXEL Technologies

    JavaScript / TypeScript Developer

    Islamabad, Pakistan

    • Developed scalable backend services and APIs for high-traffic SaaS and enterprise platforms including cloud-based CAD and VR tools
    • Built real-time communication systems using WebSockets
    • Contributed to Alibaba Cloud infrastructure including ECS provisioning, VPC configuration, OSS for 3D asset delivery, and Nginx reverse proxy setup
    • Mentored junior developers and enforced clean architecture across the team
    • Vue
    • JavaScript
    • TypeScript
    • React
    • Three.js
    • Node.js

Certifications

Education

COMSATS University Islamabad

BS, Computer Science

2018 — 2022 · CGPA 3.19

Relevant coursework

  • OOP
  • DSA
  • DBMS
  • Operating Systems
  • AI
  • Machine Learning

03What I Do

Three layers, one engineer.

Most of my work sits where these overlap — an AI capability that needs a real product around it, and infrastructure solid enough to run it unattended.

01

AI & LLM Systems

Applied AI that holds up in production — grounded, evaluated, and wired into real product flows.

  • RAG pipelines with pgvector, embedding generation, and structured output validation
  • Claude and OpenAI integrations with prompt engineering and explainable outputs
  • Voice AI on Retell, Twilio, ElevenLabs, and Deepgram with sub-second latency
02

Full-Stack Product

End-to-end product engineering, from schema design to deploy. Typed, tested, and maintainable.

  • Multi-tenant SaaS on Next.js, NestJS, Spring Boot, and PostgreSQL
  • React Native apps shipped to the App Store and Play Store at scale
  • Payments, auth, and third-party integrations: Stripe, OAuth, DocuSign, Zoom
03

Backend & Infrastructure

The systems underneath: event-driven, fault-tolerant, and built for compliance-grade workloads.

  • Microservices, queue systems (BullMQ, RabbitMQ), and event-driven architecture
  • AWS and Azure infrastructure with Docker, Kubernetes, Terraform, and CI/CD
  • Banking-grade pipelines: SFTP processing, reconciliation, and audit trails

04Stack

What I build with.

Tools I've shipped production systems on — not a list of things I've read about.

Frontend

  • React
  • Next.js (App Router)
  • Vue.js
  • Angular
  • TypeScript
  • Tailwind CSS
  • shadcn/ui
  • React Native (Expo)

Backend

  • Node.js
  • NestJS
  • Express.js
  • Java Spring Boot
  • Python FastAPI
  • Prisma

AI & LLM

  • Claude API
  • OpenAI API
  • RAG pipelines
  • pgvector
  • LangChain
  • Embeddings
  • Prompt Engineering
  • Retell AI
  • Twilio
  • ElevenLabs
  • Deepgram

Databases

  • PostgreSQL
  • MongoDB
  • MySQL
  • Redis
  • DynamoDB
  • Firebase
  • Supabase

Cloud & DevOps

  • AWS Lambda
  • S3
  • ECS
  • RDS
  • API Gateway
  • SES
  • Transcribe
  • Bedrock
  • EventBridge
  • Secrets Manager
  • Azure App Services
  • AKS
  • Azure Functions
  • Data Factory
  • Docker
  • Kubernetes
  • GitHub Actions
  • Terraform
  • Vercel
  • Railway

Integrations

  • Stripe
  • WebSockets
  • Webhooks
  • REST APIs
  • GraphQL
  • SFTP
  • BullMQ
  • RabbitMQ

05About

Who you'd be working with.

I'm a senior full-stack developer and AI engineer based in Islamabad, Pakistan with over 5 years of experience building production software. I've shipped SaaS platforms, fintech backends, AI-powered systems, and consumer mobile apps across industries including healthcare, real estate, and financial services.

I'm the founder of Aventrex Digital, a product-focused software development agency, and I freelance independently on Upwork with a 100% Job Success Score across 13+ contracts.

I work across the full stack — from database schema design to cloud deployment — and I integrate AI into real products, not demos. I use Claude Code and Cursor as primary development tools and ship faster because of it.

When I'm not building, I'm thinking about system design, real estate investment, and financial markets.

Visit Aventrex Digital
Rehan Ashraf
Based in
Islamabad, PK
Timezone
GMT+5 · US/EU overlap
Founder of
Aventrex Digital
Currently
Senior Platform Engineer, SobrietyHub

06How I Work

Predictable from scope to support.

No surprises on cost, timeline, or what you get at the end. This is the same process whether it's a two-week build or a six-month engagement.

01

Scope

We pin down the outcome, the constraints, and what's actually in v1. You get a written plan and an estimate before any code is written.

02

Build

Short feedback loops and working software early. You see progress every week — no black boxes, no month-long silences.

03

Ship

Tested, deployed, and documented on real infrastructure with CI/CD, monitoring, and handover notes your team can act on.

04

Support

I stay on after launch to monitor, fix, and extend. The codebase is structured so the next feature isn't a rewrite.

07FAQ

Questions I get before we start.

What kind of projects do you take on?

Production software with a real user at the end of it: SaaS platforms, AI and RAG systems, voice AI, fintech backends, and cross-platform mobile apps. I'm most useful on projects that need both the AI layer and the product engineering around it.

Do you work solo or with a team?

Both. Most engagements I handle end to end myself. For larger scopes I bring in senior developers through Aventrex Digital, my agency, and stay directly responsible for architecture and delivery.

How do you handle AI features that need to be reliable?

Retrieval before generation, structured output validation on every response, and grounding so answers trace back to source data. That's the difference between a demo and something you can put in front of customers.

What are your timezone and availability like?

I'm in Islamabad (GMT+5) and overlap comfortably with both EU and US mornings. I'm available for freelance and contract work, and I reply to every serious inquiry — usually within a day.

Can you work with an existing codebase?

Yes. A good share of my work is joining a live system: fixing what's fragile, extending what works, and leaving the architecture better documented than I found it.

How do engagements usually start?

A short call to understand the problem, then a written scope with milestones and a fixed estimate. You know the plan and the cost before the first commit.

08Contact

Tell me what you're building.

Send over the problem and any constraints you already know about. I reply to every serious inquiry, usually within a day, and the first step is always a short call — no pitch deck.

Islamabad, Pakistan · GMT+5 · overlaps EU and US mornings