You will get SaaS developer | React | Next.js | Node.js | Typescript Development | Web
Top Rated
Top Rated
Project details
You’ll get a complete SaaS web application build — from pixel-perfect frontend to scalable backend — delivered by a full stack developer / engineer who cares about speed, clarity, and long-term maintainability.
I build modern platform products: dashboards and SaaS system solutions using React, Next.js / Nextjs, JavaScript, Typescript, and MERN, backed by Node / Node.js APIs (and NestJS when you need enterprise structure). Expect clean architecture from a hands-on architect: secure auth & roles, multi-tenant-ready setup, subscriptions/payments, integrations, production-ready deployment, and a codebase that’s easy to extend.
Perfect for a new MVP, internal admin dashboard, or full customer-facing web app. Clear communication, milestones, and support through launch.
Let’s connect on Upwork Chat to discuss your project. I offer consultations, clear pricing, and a detailed project timeline. Unlock the full potential of React, Next.js / Nextjs, JavaScript, Typescript, MERN, Node / Node.js, and NestJS today!
📞 Reach out now for a consultation!
I build modern platform products: dashboards and SaaS system solutions using React, Next.js / Nextjs, JavaScript, Typescript, and MERN, backed by Node / Node.js APIs (and NestJS when you need enterprise structure). Expect clean architecture from a hands-on architect: secure auth & roles, multi-tenant-ready setup, subscriptions/payments, integrations, production-ready deployment, and a codebase that’s easy to extend.
Perfect for a new MVP, internal admin dashboard, or full customer-facing web app. Clear communication, milestones, and support through launch.
Let’s connect on Upwork Chat to discuss your project. I offer consultations, clear pricing, and a detailed project timeline. Unlock the full potential of React, Next.js / Nextjs, JavaScript, Typescript, MERN, Node / Node.js, and NestJS today!
📞 Reach out now for a consultation!
Programming Languages
HTML & CSS, JavaScript, TypeScriptCoding Expertise
Cross Browser & Device Compatibility, Performance Optimization, DesignWhat's included
| Service Tiers |
Starter
$299
|
Standard
$4,999
|
Advanced
$19,999
|
|---|---|---|---|
| Delivery Time | 3 days | 30 days | 70 days |
Number of Revisions | 0 | 1 | 2 |
Number of Pages | 1 | 2 | 3 |
Design Customization | - | - | |
Content Upload | - | - | |
Responsive Design | - | ||
Source Code | - |
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MK
Marshall K.
May 19, 2026
Javascript and Auth Optimization
Oleksandr did a great job explaining where my app needed improvement. He walked me through the steps I needed to take my app to the next level.
TS
Taj S.
Mar 25, 2026
React Native Developer for AI App Build Out
Everything in our project was delivered with very high quality and on time. Pleasure to work with Oleksandr and the team. Very good communication on the project and great project management. Very talented professional
MS
Musa S.
Mar 19, 2026
Mobile App Development | React Native Mobile Developer (iOS & Android)
Project was completed smoothly with no issues. Great work as usual. 10/10 work.
TL
Taras L.
Oct 3, 2025
React Native developer for cute mobile app [longterm]
Super smart, thinks with you, comes up with own ideas, code works great and stable.
Very friendly and keeps his word. A dream of a freelancer!
Highly recommend!
Very friendly and keeps his word. A dream of a freelancer!
Highly recommend!
LD
Laurent D.
Sep 26, 2025
AI Coach App — React Native (React, Redux Toolkit, TypeScript) + Python/FastAPI Backend
About Oleksandr
Mobile App Developer | React Native + AI | iOS & Android
100%
Job Success
Lviv, Ukraine - 3:51 pm local time
I run engagements as a long-term technical partner, not a vendor you chase for updates - which is why several engagements have run 16 months to 4+ years. You get senior engineering ownership from first call to store release: clear scope, milestone-based delivery, honest timelines, and a lead who is accountable for the result. As founder and lead engineer, I make sure the mobile app development gets done right, not just fast.
WHAT WE BUILD
- Full mobile app development in React Native and Expo, from idea to store release - a cross-platform iOS and Android app from one codebase, typically a launched MVP in 6-10 weeks. With a senior React Native developer leading, we cover MVP development, App Store and Google Play submission, and everything in between.
- AI integration inside mobile apps - chat, image and vision analysis, and conversational voice (OpenAI and Anthropic Claude), already shipped in live AI mobile apps. Clean API integration so the AI feature feels native, not bolted on.
- Rescue and refactor of React Native apps that broke under real users - performance, crashes, and stability work to get an existing app back to store-ready.
- Backend when your app needs more than screens: Node.js, NestJS, Python and FastAPI, PostgreSQL, MongoDB, Firebase, and Supabase (including auth and RLS).
WHO IT IS FOR
- Starting from scratch: a clear path from idea to a launched MVP in 6-10 weeks, built by a team that has shipped to both stores.
- Already have an app: mobile app development help with new features, performance, and stability - whether you need an iOS developer, an Android developer, or both.
- Want to add AI: a chat, vision, or voice feature shipped into your live cross-platform app through careful AI integration, scoped so it ships fast and stays maintainable.
HOW WE WORK
You talk to the people building your app, not a sales layer. We agree on scope and milestones up front, you see working builds early and often on TestFlight and internal tracks, and you get honest status instead of silence. When something is harder than estimated, you hear it early - with options, not surprises. The goal is a stable app you can grow on, and a codebase your next mobile app developer can read without a rewrite.
VERTICALS WE KNOW
We have shipped mobile app development work across health and wellness, nutrition, and fitness (calorie tracking, meal analysis, AI coaching), fintech and Web3 (payments, Plaid, Polygon on-chain apps), SaaS (Stripe billing and dashboards), and internal tools and logistics (warehouse and operations systems). If your app lives in one of these spaces, we have built and launched something close to it.
RESULTS
- An AI nutrition tracker - React Native meal and calorie analysis with Anthropic Claude and OpenAI - live on both the App Store and Google Play, owned end to end (mobile, API, and admin).
- An AI fitness app on a Python and FastAPI backend with OpenAI, live on the App Store and Google Play.
- A conversational-voice health app built with React Native, Expo, and Claude.
- A Web3 scratch-card app on Polygon with Plaid integration, live on Google Play, plus a daily-quotes app on the App Store.
- A warehouse operations system that runs 4x faster for 100+ employees.
- Long-term mobile app development engagements kept for 16+ months and 4+ years - the clearest signal that this work lasts.
OUR STACK
React Native, Expo, TypeScript for cross-platform iOS and Android; Node.js, NestJS, Python and FastAPI, PostgreSQL, MongoDB, Firebase, and Supabase on the backend; Stripe, in-app purchases, push notifications, and WebSockets for real product features; and AI APIs (OpenAI and Anthropic Claude) for chat, vision, and voice. This is the full toolkit for modern mobile app development and AI integration, from first commit to a stable app on the App Store and Google Play.
Send me your idea or your existing app and you will get back a clear, honest breakdown - what to build first, what can wait, and a realistic timeline for the mobile app development. No pressure, no jargon, just a straight answer from the lead who would own the work.
Oleksandr - founder and lead engineer, Kultrix (AI and Mobile App Studio).
Steps for completing your project
After purchasing the project, send requirements so Oleksandr can start the project.
Delivery time starts when Oleksandr receives requirements from you.
Oleksandr works on your project following the steps below.
Revisions may occur after the delivery date.
Review provided materials
Prepare detailed work breakdown structure for the further implementation