Marcus Kim · Freelance app developer
Hire me to fix, finish, or ship your app.
I help founders turn app ideas, existing code, and unfinished products into working mobile and web experiences. I can scope the work, build the user journey, connect the backend, test the result, and prepare it for release.
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Bring me the part keeping your product from moving.
MVPs and features
Turn a requirement, design, or rough idea into one complete working user journey.
UI implementation
Translate approved screens into a responsive interface without burying the product in generic cards.
Backend integration
Connect authentication, databases, storage, realtime behavior, and external services with Firebase or Supabase.
QA and release prep
Trace stubborn bugs, verify the real workflow, and prepare a stable build for TestFlight, stores, or the web.
Selected work
Five products. Five different jobs to be done.
These are working app captures, not static mockups. Press play to see the real interaction.
SwiftUI · Supabase · Maps
What’s The Move
An event-based social product built with a startup team. The app combines a social feed, search, maps, and location-aware discovery so people can find what is happening nearby.
My work: iOS implementation, feature ownership, engineering coordination, and iterative demos.
SwiftUI · Firebase · Social workflows
DragSet
A social app for car enthusiasts to discover other drivers, message one another, organize races, and host events. It brings profiles, discovery, chat, and event coordination into one product.
My work: solo product development, Firebase backend management, interface implementation, QA routes, and client demos.
React Native · Expo · Firebase
InvoiceKit
A mobile invoicing product designed around the full lifecycle of a small-business invoice: create, revise, track, record payment, and understand the cost breakdown.
My work: product workflow, Expo and React Native implementation, Firebase authentication, invoice states, and mobile QA.
SwiftUI · StoreKit · Native iOS and iPadOS
NameSnap Picker
A native random picker for teachers, streamers, coaches, parties, and groups. Paste a list, choose Quick Pick or Spin Wheel, avoid repeats, and keep a visible winner history without turning a simple decision into a fiddly workflow.
My work: product and visual design, SwiftUI implementation, iPhone and iPad layouts, 300 celebration combinations, interaction polish, TestFlight, and App Store delivery assets.
UIKit · AudioKit · Firebase · MIDI
FourBrains
A rhythm-training prototype that turns independent limb coordination into an interactive grid. The visual system stays out of the way while audio and timing feedback do the teaching.
My work: solo concept, UIKit interface, AudioKit and MIDI integration, Firebase support, and interaction design.
How I work
A working slice beats a month of invisible progress.
Clarify the user, main job, current code, dependencies, and definition of done.
Complete one real journey from interface through backend instead of scattering partial work.
Show the running product at meaningful checkpoints so feedback stays attached to evidence.
Test the actual workflow, fix the category of failure, and prepare the release path.
Marcus Kim | AI App Builder 