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Zafer Çağatay Umut

Full-Stack Software Engineer

From complex systems to products people use.

I build and own production SaaS, AI-enabled applications, and mobile products from interface and APIs to deployment.

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Based in Türkiye. Working worldwide.

Remote worldwide · B2B / independent contractor

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Explore the productsIstanbul, TR UTC+3

Selected work

Production products across business software, mobile, and internal operations.

Karta finance and CRM workspaceKarta AI CFO financial analysis example
01Production B2B SaaS

Karta

Multi-tenant finance and CRM SaaS with AI-powered analysis.

Role
Full-Stack Developer / Product Engineer

Took over an existing codebase and developed it into a production product; owned frontend, backend, tenant isolation, RBAC, integrations, and deployment.

Tenant isolation and role-based access control.

  • Next.js
  • TypeScript
  • Express
  • PostgreSQL
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Pavlov daily pet-care home screenPavlov AI pet assistant conversation
02iOS & Android

Pavlov Pet Care

Production pet-care app for iOS and Android.

Role
Co-Founder & Full-Stack Developer

Built mobile and backend systems, AI features, subscriptions, notifications, offline synchronization, and releases.

Offline-first SQLite synchronization.

  • React Native
  • Expo
  • Node.js
  • PostgreSQL
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System overview: operational data, internal platform, recurring workflows

System overview · Not a product screenshot

03Internal business software

Business Operations Admin Platform

Internal software centralizing operational data and automating recurring work.

Role
Full-Stack Developer

Full-stack development of the production internal platform.

Centralized operational data and recurring workflow automation.

  • .NET Web API
  • C#
  • React/Next.js
  • TypeScript

Internal production platform

System overview: admin and client dashboards, activity tracking, payouts

System overview · Not a product screenshot

04Tracking & payout workflows

Affiliate Marketing Platform

Admin and client dashboards for tracking activity and managing payouts.

Role
Full-Stack Developer

Built the platform from the ground up.

Real-time registration, deposit, and conversion tracking.

  • Node.js
  • React
  • MySQL

Internal production platform

A product problem.A path to production.

I turn requirements into interfaces, systems, running software and keep improving what ships.

Product thinking. Full-stack implementation. Ongoing ownership.

  1. Understand the problem

    Start with the user flow, the constraints, and the first useful version.

    A clear scope
    User needUser flowConstraints
    First version
    StartActionResult
    A complete user flow

  2. Plan the system

    Shape the experience, API boundaries, and data ownership before implementation.

    An intentional structure
    User flow
    InterfaceAPI contractData model

  3. Build the interface

    Make the product work across screens, devices, and every interaction state.

    A usable web or mobile product
    User action
    ReadyLoadingEmptyError

  4. Build the core

    Connect the interface to validated APIs, business rules, and reliable data.

    A working vertical slice
    ValidateAuthorizeBusiness logic
    Schema · Integrity · Data boundaries

  5. Connect the services

    Integrate the capabilities the product needs, with clear boundaries.

    One connected system
    Product
    AIPaymentsStorageNotifications

  6. Test and refine

    Follow real user journeys. Find the broken edges. Make the experience hold up.

    Ready beyond the happy path
    User flowsEdge casesDevicesAccessibilityPerformanceRegressions

  7. Ship to production

    Move from local development to configured environments and repeatable releases.

    Running software
    ConfigureMigrateRelease
    Web / mobile / cloud

  8. Observe and improve

    Turn production issues and user feedback into the next useful change.

    The next iteration
    Logs + feedbackDebug + improve
    Next requirement
One product, built layer by layer.The complete system01 / 08Understand the problem
Product requirementUser flow + first useful version
Product experience
Web / mobile interface
Responsive · loading · empty · error
Application layer
APIAuth + permissionsBusiness logic
Data model
Relationships + integrityAccess + data boundaries
Local / offline where needed
Integrations
AIPaymentsStorageNotifications
As the product needs
Test + refineUser flows · edge cases · devices · performance
ProductionEnvironment → migrations → release
Logs → debug → improveBack to the next requirement
A general workflow; the architecture follows the product.

The release is a milestone.Ownership continues.

Real usage → feedback → the next iteration

A practical stack for shipping products.

Frontend
React, Next.js, TypeScript, Tailwind
Product interfaces
Backend
Node.js, Express, .NET Web API, C#
APIs and business logic
Mobile
React Native, Expo
iOS and Android
Data
PostgreSQL, MySQL, SQLite
Multi-tenant and offline data
Infrastructure
Docker, Linux, Nginx / Traefik, Vercel, AWS
Deployment and operation
AI and integrations
AI / LLM APIs, payment integrations, third-party APIs
Product workflows

Building, shipping, and staying responsible.

2022–Present

Independent Software Developer

Production SaaS, mobile products, and internal business platforms. Product engineering and ongoing ownership across Karta, Pavlov and more.

2021–2022

Full-Stack Development Intern

Mivento Bilişim A.Ş.

Frontend improvements, API integrations, debugging, performance work, and end-to-end testing with senior developers.

B.Sc. Software Engineering · Istanbul Aydın University · 2019–2025

Turkish · Native / English · B2

Resume

Have a product to build or a system to improve?

Let’s talk about the product, the engineering, and what needs to ship.

Remote worldwide · B2B / independent contractor · UTC+3

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