Custom software development servicesA website for your business.
Your mobile app for iOS and Android.
App369 builds both, plus the backend, payments and AI features behind them, for startups and small businesses, from Miami, Florida.
Under the hood: Vue, Nuxt and React on the web; Flutter and Swift for iPhone and Android; Node.js, TypeScript and Firebase on Google Cloud behind them.
- Fiverr
- 5.0 · 127 reviews
- Own product
- Workspace369
- Fixed-price offers from
- $450
AI implementation
AI that answers your leads and handles the repeat work
For clinics, law firms, agencies, SaaS teams and real estate offices: one channel or one workflow at a time, at a fixed price, in code and accounts you own.
AI Implementation
Custom AI development for your business, one fixed-scope piece at a time: AI features and agents with a one-page spec and a scored eval run, integrations, all in accounts you own.
- Custom AI
- AI Features
- Agents
- Evals
AI Receptionist
Calls, chat and web forms answered 24/7, leads qualified and booked on your calendar, and a person brought in with a summary. Missed-call text back is its own fixed-price piece.
- Answering
- Booking
- Missed-Call Text Back
- Twilio
AI Answering Service
Calls answered day and night on your own number, the message taken or the appointment booked, and missed calls texted back. Built once at a fixed price instead of a plan sized by calls.
- After Hours
- Your Own Number
- Messages
- Twilio
Speed to Lead
Missed calls texted back, web form leads answered with a booking link, and every lead routed to the right person and logged in your CRM.
- Missed-Call Text Back
- Lead Routing
- AI Follow-Up
- Twilio
AI Automation Services
One repeated task at a time automated inside your own tools: lead intake, document extraction, email triage, syncs and reports, tested and logged.
- Workflow Automation
- Document Extraction
- Email Triage
- Integrations
AI for Accountants
An AI email assistant for accounting, tax and bookkeeping firms: client email labeled, routine replies saved as drafts, and nothing sent without a person.
- Gmail
- Microsoft 365
- Drafts Only
- Fixed Price
Chatbot Development
An AI chatbot for your website, your app or your staff that answers from your own pages and documents, built to link the page behind each answer and hand off to a person.
- Website Chat
- Help Assistants
- Internal Knowledge
- Hand-Off
AI Agent Development
One AI feature or agent built in 10 business days from a spec you approve, with tools limited to approved actions and a scored eval run before handover.
- AI Agents
- LLM Features
- Eval Sets
- MCP Connectors
AI Consulting
Paid consultations on what to automate first, a written quote for the build, then a fixed-price build from the same developer.
- Written Scope
- Paid Consultations
- Fixed Price
Apps and platforms
Mobile apps, web apps and the backend behind them
The product itself: iPhone and Android apps, websites and SaaS, APIs and payments, design, search and the upkeep after launch.
Mobile App Development
iOS and Android apps in Flutter or native Swift, from a first release to fixing an app that already has users.
- iOS App Development
- Android App Development
- Flutter Cross-Platform Apps
- App Store Optimization
Web Development
Web applications built with Vue.js and Nuxt, server-rendered for fast first loads.
- Custom Web Applications
- E-Commerce Platforms
- Progressive Web Apps (PWA)
- API Development
SaaS Development
A first SaaS version in about 4 weeks from a signed quote, with Stripe subscriptions, sign-in and roles, and the integrations your customers ask for.
- Web App MVP
- Stripe Subscriptions
- API Integrations
- MCP Connectors
Backend & API Development
APIs, data models, background jobs and security rules in Node.js and TypeScript on Firebase and Google Cloud.
- REST APIs
- Firestore Data Models
- Background Jobs & Queues
- Security Rules & Cloud Cost
Payments & Integrations
Stripe billing and checkout, Twilio texting and calls, email and calendar integrations, tested before real money moves.
- Stripe Subscriptions & Checkout
- Stripe Connect Payouts
- Twilio SMS & Voice
- Email & Calendar APIs
SEO, GEO & AEO
Found and quoted by Google and by AI assistants: citation audits, structured data, answer pages and AI crawler rules, at fixed prices.
- AI Citation Audits
- Structured Data
- Answer-Ready Pages
- llms.txt & Crawler Rules
UI/UX Design
Research-driven design in Figma that delivers measurable results.
- User Interface Design
- User Experience Design
- Wireframing & Prototyping
- Design Systems
Technical Consulting
Consultations help you choose the right stack and strategy before you invest.
- Technology Stack Selection
- Architecture Planning
- Code Review & Audit
- Digital Transformation
Maintenance & Support
App369's support plans include bug fixes, security patches, OS updates, and crash and uptime monitoring, with critical issues handled first.
- Bug Fixes & Updates
- Performance Optimization
- Security Patches
- Crash & Uptime Monitoring
Prefer a fixed price?
Fixed scope, fixed price, paid upfront. The work happens in writing; no call needed.
- App Fix Ticketfrom $450One reproducible bug in an existing mobile or web app, diagnosed and fixed.
- AI-Built App Rescuefrom $450A Lovable, Bolt or Cursor app checked end to end in 3 days, then its worst problems fixed at a fixed price.
- Web App MVP Sprintfrom $6,000A scoped web app MVP in Vue/Nuxt or React, with a fixed quote after a $450 written scoping.
- Monthly Dev Subscriptionfrom $1,495/monthOne development request at a time, most back in about 2 business days. Pause or cancel anytime.
Data and research
- Fixed-Price App Development Prices 2026
What sellers publish for a bug fix, Stripe subscriptions, a rules audit, an AI-built app rescue and a web MVP.
- App Development Statistics 2026
App Store and Google Play economics, store fees and review times, mobile OS share and framework usage, each sourced.
Start here
Start with your project
Describe your project and receive a technical assessment by email, usually within one business day. Prefer to talk? Consultations are $100 per 15 minutes, paid upfront.
Fiverr reviews / 95 on app work
What buyers said about this kind of work
“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!”
A buyer in 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.”
A buyer in the United States, July 2024. Custom order on Fiverr “Had a great consultation with Szymon. He knows his stuff and I have a deeper understanding of how my new mobile app can work.”
A buyer in the United States, April 2024. Custom order on Fiverr
Read the whole story
- Sixteen five-star reviews from one buyer: mobile apps, app design and a Shopify store (Mark, United States)
- A large custom app build, delivered on the back end and the front end (A buyer in the United States)