Custom app development · Palm Beach County, Florida Know your price
before you hire.

Mobile apps, web apps, backends, AI features and Stripe payments, at fixed prices or a fixed written quote. Built by Simon Dziak in Boynton Beach, and you own the code.

Fiverr: 5.0 · 126 reviews
Own product: Workspace369
Offers from: $450

All 12 fixed-price offers →View portfolio →

Instant quote · about a minute

What can we help you build?

Tap one to start. Prices shown are where projects start.

A mobile appfrom $9,000 A web appfrom $6,000 Web and mobilefrom $9,000 Add AI to my product$2,500 fixed Set up payments$950 fixed Connect two tools$1,200 fixed Fix something brokenfrom $450

Brands in our portfolio

BILSTEIN

Chicago Pneumatic

Gavalina

SaLT Jewelry

BILSTEIN

Chicago Pneumatic

Gavalina

SaLT Jewelry

Palm Beach County based

5.0

126 Fiverr reviews

Full stack

Mobile, web, backend & AI

50/50

Upfront & on delivery

Eastern Time hours

What App369 builds

One senior developer across the whole product: the app, the web front end, the backend, the AI features and the payments. Pick the tool that fits the job, not the other way round.

Mobile apps

iOS and Android apps, from a first release to fixing one that already has users.

Flutter, Swift, App Store & Google Play

Fixed price: App Fix Ticket (from $450)

Web apps and sites

Customer portals, dashboards, SaaS front ends and fast marketing sites.

Vue, Nuxt, React, TypeScript

Backends and APIs

The server side: data models, APIs, background jobs, security rules and cloud cost.

Node.js, TypeScript, Firebase, Google Cloud

Fixed price: Firebase Security Rules Audit + Fix PR ($950), Firebase Cost-Cut Audit ($750)

AI features and agents

LLM features inside your product, tool-using agents, and MCP servers for Claude and ChatGPT.

Claude, Gemini, MCP, Evals

Fixed price: MCP Connector for your SaaS ($2,500)

Payments and integrations

Subscriptions, checkout, payouts, texting, email and calendar, wired up and tested.

Stripe, Twilio, SendGrid, Webhooks

Shopify stores

Theme work, speed fixes and cleaning out code left behind by old apps.

Shopify, Liquid, Core Web Vitals

Fixed price: Shopify Speed & Checkout Tune-Up ($750)

Product video

Launch videos and Shorts built from your real product screens.

Remotion, Motion graphics, YouTube Shorts

Fixed price: SaaS Launch Video ($1,500), Shorts-as-a-Service ($1,500/month)

Rated 5.0 across 126 Fiverr reviews

Simon’s Fiverr seller profile, as of October 2026: app builds, Shopify work, app design and custom projects since 2020. Every review is public on Fiverr, and all 126 are copied word for word on our reviews page.

Read the reviews on Fiverr See all reviews here

“Working with Simon makes everything run so smoothly and better than I could ask for it. Amazingly communicative, extremely knowledgeable of coding and the backend processes. I strongly recommend.”
drewbirchvoice, United States, January 2026. App development on Fiverr
“Working with Simon has been an absolute pleasure. He’s not only incredibly skilled with his code, but he also brought so much care and attention to detail, especially when creating a custom section template for my Shopify site. He made the entire process smooth and collaborative, and consistently went above and beyond to make sure everything looked and functioned beautifully, very much the way I've envisioned. Highly recommend him for anyone looking for thoughtful, top-notch development support!”
anacarini, China, April 2025. Custom order on Fiverr
“Very detailed and professional. Understands full scope of project before advancing and has honest but critical feedback. such a pleasure with consultation and can't wait to get started.”
kendrickmyles, United States, July 2024. Custom order on Fiverr
“2nd time using Simon and again knocked it out the park great price and fast delivery I no longer need to look for anyone else he's my guy when comes to the services he provides A+ 10 stars”
brnxbmr86, United States, November 2023. Shopify on Fiverr
“Great work! Szymon helped our mobile app concept come to life and we are very pleased with the outcome. He was great to communicate with throughout the process, making himself available when I needed him, and was quick to respond to feedback. We will definitely use him again. Thanks Szymon!”
rebeccamorris28, United States, June 2022. App development on Fiverr
“Syzmon is a very hard working and technically nimble developer. He works day and night to complete the work. This was a large project and required adjustments along the way and Syzmon was flexible and helped discover optimal solutions and adjusted as we learnt better solutions.”
nebo0373, United States, July 2022. App development on Fiverr

Our Services

Custom iOS and Android apps built to be easy to use, reliable, and scalable. Whether it's a personal project, startup, or enterprise tool, App369 turns your idea into a production-ready application.

AI automation reduces manual work and operating costs. App369 identifies where AI fits your workflows — from document processing to customer support — and builds custom solutions integrated into your existing systems.

A website is essential for any idea you want to share with the world. We build modern, responsive websites that work smoothly across all devices, helping you connect with your audience and bring your idea to life online.

Once your app or website is launched, we offer ongoing maintenance services on an a la carte basis. Whether you need updates, improvements, or support, we're here to keep your app running smoothly as your business evolves.

Work Directly with the Senior Developer Who Builds Your App

At App369, our founder and head developer personally leads every project. Unlike larger firms where projects are often delegated to junior team members, you work directly with the senior engineer who builds your app, from start to finish.

By working closely with the owner, you can be confident that your project will receive the highest level of care, attention to detail, and innovative solutions tailored to your unique requirements.

Our goal is not just to deliver a product but to create an exceptional development experience where your vision is brought to life with precision, dedication, and the expertise it truly deserves.

From Idea to Launch in 8-12 Weeks

Understanding Your Idea

We start by listening to your idea and understanding your goals, then we create a plan to bring your idea to life.

Design & Development

We design and build your app or website with you in mind, making sure it's easy to use, visually appealing, and works on all devices.

Launch & Support

Once your app or website is ready, we launch it and continue to provide support, making sure it works flawlessly as your idea grows.

Fixed-price services

Fixed scope, fixed price, paid upfront. The work happens in writing; no call needed.

Selected work / since 2020

Apps, AI and platforms we've shipped

All 21 projects →

2023–now · Our own product

Workspace369

SaaS, iOS & web

An all-in-one workspace for service businesses: CRM, proposals, invoicing and payments, scheduling and a shared email, SMS and voice inbox. Designed, built and run by App369.

Flutter app on iOS and the web, live on the App Store
Firebase backend split into 20+ Cloud Functions codebases
Stripe billing, Twilio voice and SMS, inbound email security

FlutterFirebaseTypeScriptStripeTwilio

Case study →App Store ↗ Fixed price: MCP Connector for your SaaS ($2,500), Workspace369 setup, done for you (from $450)

2026 · Our own product

3693

Music app

A private music app: search, a now-playing screen with background playback, a queue, playlists, liked songs, a cloud library and listening stats, in dark and light themes.

Background audio with a managed playback queue
Typed Cloud Functions backend behind Firebase Auth
Automated walkthrough that screenshots every screen in both themes

FlutterFirebaseTypeScriptjust_audioHive

Case study →

2026 · Open source by Simon Dziak

SaaS MCP Connector

AI integration

An MCP server that lets Claude use a SaaS API safely: every call is scoped to the signed-in user's workspace, writes are gated, and outbound HTTP is rate limited.

TypeScriptMCPClaude

Case study →GitHub ↗ Fixed price: MCP Connector for your SaaS ($2,500)

2021 · Our own R&D

Deep Dream

AI image app

Our first AI build. A Flutter app sends a photo to a Python API, a queue worker runs DeepDream on a convolutional neural network, and the dreamed image comes back to save to the gallery.

PyTorch DeepDream across several CNNs (VGG, ResNet, GoogLeNet)
Flask API with token auth and a Redis job queue
Style and parameter controls in the app

FlutterPythonPyTorchFlaskRedis

Case study →

Client project

BILSTEIN

Mobile & web app

An app for finding, configuring and choosing BILSTEIN suspension products for a given vehicle, on mobile and the web.

MobileWeb

BILSTEIN ↗

2023 · Client project, built by Simon

Bull Horn GPS Alarm

Mobile app

A remote control for GPS vehicle and asset alarms. Each alarm is saved once with its number and password, then every command is a single tap instead of a cheat sheet of SMS codes.