# Simon Dziak
> Simon Dziak (Szymon Dziak) is the founder and lead developer at App369. Builds mobile apps, web platforms, and AI features from Miami, Florida.
Canonical: https://app369.com/about/szymon-dziak/
Software engineer and founder of App369, building mobile apps, web apps, backends, AI features and payments.
[LinkedIn](https://linkedin.com/in/szymondziak) [X (Twitter)](https://x.com/szymondziak)
My story
## **Background**
I started writing code at 14 and never stopped. After more than a decade of building software for startups and enterprises across healthcare, fintech, e-commerce, and education, I founded App369 to help businesses turn ambitious ideas into production-ready applications.
My approach is hands-on. I still write code daily, review every architecture decision, and stay deeply involved in every project we deliver. I believe the best software comes from teams where leadership understands the technical details, not just the business strategy.
Based in South Florida, I work with clients across the United States and internationally, building mobile apps, web platforms, and custom software that drives real business outcomes.
What I build
## **Areas of expertise**
Deep technical expertise across the full software development lifecycle.
### **Mobile Development**
Cross-platform and native mobile apps for iOS and Android. Built with Flutter, Swift or Kotlin, chosen to fit the product.
- Flutter
- Swift
- Kotlin
- Dart
### **Web Development**
Full-stack web applications, SaaS platforms, and progressive web apps. Building performant, SEO-optimized web experiences with modern JavaScript frameworks.
- Vue.js
- Nuxt
- React
- TypeScript
### **Cloud & Backend**
Scalable backend architectures, API design, and cloud infrastructure. Experience with real-time databases, serverless functions, and enterprise-grade deployments.
- Node.js
- Firebase
- Google Cloud
- Python
Industries
## **Industry experience**
Hands-on project leadership across high-regulation and high-growth verticals.
### **Healthcare**
HIPAA-compliant patient portals, telehealth platforms, EHR integrations, and clinical workflow tools. Understanding of healthcare data regulations and interoperability standards including HL7/FHIR.
### **Fintech**
Payment processing apps, digital banking platforms, investment portfolio tools, and insurance claims systems. Experience with PCI DSS compliance and financial data security.
### **E-Commerce**
Custom storefronts, Shopify integrations, marketplace platforms, and mobile commerce apps. From product catalogs to checkout flows to inventory management.
### **Education**
Learning management systems, student engagement platforms, virtual classroom tools, and EdTech SaaS products. Accessible, inclusive design for diverse learner populations.
On video
## **Watch Simon**
Simon's App369 intro (October 2026, 1 minute), and "Is App Development For You?", from his YouTube channel in April 2024 (8 minutes).
Writing
## **Recent articles**
Insights on app development, technology strategy, and the software industry.
[Development Costs·November 9, 2026·8 min**Android App Development Cost (2026)**
Android app development cost in 2026, worked from the BLS median developer wage, plus Google Play costs only Android has: a 25 USD fee, testing, API updates.](https://app369.com/blog/android-app-development-cost-2026/)
[Development Costs·November 8, 2026·8 min**Custom CRM Development Cost (2026): Agency Prices Compared**
Custom CRM development cost in 2026: agencies publish $15,000 to $100,000 for a first version. App369 builds one from $6,000 after a $450 written scoping.](https://app369.com/blog/custom-crm-development-cost-2026/)
[AI & Technology·November 8, 2026·8 min**How Much Does Firebase Cost in 2026? Prices and 3 Examples**
What Firebase costs in 2026: Spark and Blaze free limits, Firestore, Cloud Functions, Hosting and Auth prices from Google, and worked bills for 3 app sizes.](https://app369.com/blog/firebase-cost-2026/)
[AI & Technology·November 8, 2026·10 min**How to Build an MCP Server in 2026: Step by Step with Code**
Build an MCP server over your existing REST API with the TypeScript SDK v2: tools, Streamable HTTP, Inspector tests and OAuth, on the 2026-07-28 spec.](https://app369.com/blog/how-to-build-an-mcp-server-2026/)
[AI & Technology·November 2, 2026·6 min**AI API Errors: 7 OpenAI, Claude, Gemini and MCP Fixes (2026)**
AI feature broken by a 401, 429 or 529, or an MCP connector that won't connect? 7 OpenAI, Anthropic, Gemini and MCP errors, what each means and how to fix it.](https://app369.com/blog/ai-api-errors-openai-claude-gemini-mcp-fixes-2026/)
[AI & Technology·November 2, 2026·7 min**App Store and Google Play Rejections: 13 Fixes (2026)**
App rejected by Apple or Google Play? 13 rejections, from Guidelines 2.1, 4.3 and 5.1.1 to Play's Data safety form and 12-tester rule, and how to fix each.](https://app369.com/blog/app-store-google-play-rejections-fixes-2026/)
[AI & Technology·November 2, 2026·6 min**Expo and Flutter Build Errors: 12 Fixes (2026)**
Expo or Flutter build failing, or the app crashes after release? 12 mobile build errors, from EAS builds and pod install to TestFlight and Gradle, and each fix.](https://app369.com/blog/expo-flutter-build-errors-fixes-2026/)
[AI & Technology·November 2, 2026·7 min**Firebase Auth Errors: 9 Sign-In Fixes (2026)**
Firebase sign-in broken? The 9 common Firebase Auth errors on web, Android, iOS and Flutter, from invalid-credential to unauthorized-domain, and each fix.](https://app369.com/blog/firebase-auth-errors-sign-in-fixes-2026/)
[AI & Technology·November 2, 2026·7 min**Firestore and Cloud Functions Errors: 11 Fixes (2026)**
Missing or insufficient permissions, a query that requires an index, a quota error or a Cloud Function that fails? 11 Firebase backend errors and their fixes.](https://app369.com/blog/firestore-cloud-functions-errors-fixes-2026/)
[AI & Technology·November 2, 2026·6 min**Lovable, Bolt and Replit Errors: 7 Fixes (2026)**
Lovable site blank after publish, a Bolt build that fails on Netlify, GitHub sync stuck or data gone after a Replit redeploy? 7 AI app builder errors, fixed.](https://app369.com/blog/lovable-bolt-replit-errors-fixes-2026/)
[**View all articles **](https://app369.com/blog/)
Start here
## **Work with Me**
Have a project in mind? I personally read every inquiry and reply by email, usually within one business day. Let's discuss your goals, technology options, and how App369 can help.
[**Get in Touch **→](https://app369.com/contact/) [**View Our Work**](https://app369.com/portfolio/)
You can also hire me through [Upwork (opens in a new tab)](https://www.upwork.com/freelancers/~01ac26258ed8033aa4).