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Sergio smiling at a café table with an espresso, Medellín
Medellín, CO · ☕
Hi! this is Sergio!

Mobile Apps Architect

iOS Android WebAgentic Engineering

Mobile experiences people love to come back to.

Apple-first, Android-ready. Ten-plus years designing and shipping iOS and Android apps — from early-stage products to apps used by millions — with an obsession for architecture that stays clean as it scales.

Let’s talk RésuméSee my work
  • 10+Years shipping mobile
  • 9Companies & agencies
  • 2Platforms, one mindset

About

Craft, architecture, and shipping — in that order.

  • Native feel, always

    Platform conventions first. Custom only when it earns it.

  • Architecture that ages well

    Unidirectional Data Flow by default — TCA, Redux, MVVM, VIPER — chosen for the team, tested from day one.

  • Ship, measure, refine

    CI/CD, analytics, and crash tooling wired in before launch.

I'm a senior mobile engineer with 10+ years focused on crafting world-class user experiences. I've worked across B2C and B2B products, and I excel at designing scalable, Offline First software architectures grounded in industry practice — Clean Code, SOLID, TDD, CI/CD — to take world-class apps all the way to the App Store and Google Play.

I care about the details Apple cares about: motion that means something, layouts that respect the Human Interface Guidelines, accessibility as a default. On Android I bring the same discipline with Kotlin and Compose. And when a team needs one codebase, I've shipped React Native at scale — including native modules that make it feel first-party.

Self-taught since childhood, still learning every week. The last couple of years I've gone all-in on generative AI: sharpening my own engineering craft with it, standing up teams of AI agents with orchestration between them to deliver faster and more efficiently, and building products end-to-end with a system of my own — from conception to shipping (name undisclosed, for now). Daily drivers: Claude Code, Swift, Xcode and JetBrains — on top of The Composable Architecture, Swift Testing and Kotlin Multiplatform.

Medellín, Colombia · Remote worldwideOpen to senior / lead mobile roles and select consulting

Sergio sitting on a step next to Maximus, his German Shepherd, at a bar in Medellín
Maximus · Chief Morale Officer 🐾

About me

Beyond the code.

I'm Sergio — Colombian, based in Medellín, and happiest somewhere between a good espresso and a well-typed codebase. I've been taking things apart and building them back since I was a kid; software just turned out to be the medium that never ran out of new things to learn.

Mornings run on discipline: coffee first (the city makes that easy) and a walk with Maximus, my German Shepherd — equal parts sidekick, code reviewer, and the reason I've gotten very good at one-handed typing — and then training, no negotiation.

Off the clock I'm a huge anime and manga advocate — I consume a lot of both — usually with film scores, J-Pop or J-Rock driving the day, plus learning Japanese one kanji at a time and the occasional deep dive into how Apple and Google think about design. If any of that sounds like your kind of conversation, say hi.

Based in
Medellín, Colombia 🇨🇴
Sidekick
Maximus 🐕
Fuel
Espresso ☕ · training 💪
Fandom
Anime & manga 🎌
On repeat
Scores · J-Pop · J-Rock 🎧
Learning
日本語 🇯🇵 · KMP

Services

At your service — on your terms.

I'm available for hire: freelance projects, direct consulting, or embedded in your team — whatever engagement works for you. This is the work companies bring me in for.

  • End-to-end mobile apps

    From conception to the App Store and Google Play: iOS (Swift, SwiftUI), Android (Kotlin, Compose) — or React Native when one codebase is the right call. Offline First, world-class UX.

  • Agentic AI delivery

    I stand up teams of AI agents with orchestration between them — Claude Code at the center — so your product ships faster and more efficiently without sacrificing engineering quality.

  • Architecture & audits

    Unidirectional Data Flow, TCA, Redux, Clean Code. I design scalable architectures from scratch, or audit the one you have and leave you a concrete refactor path.

  • Web & cross-platform

    React, Gatsby, TypeScript and Redux for the web — plus the native modules that make hybrid apps feel first-party on every platform.

  • Rescue & modernization

    Legacy migrations (Objective-C → Swift, monoliths → modules), performance and crash-rate turnarounds, accessibility hardening.

  • Team enablement

    Mentoring, code-review culture, CI/CD pipelines, and adopting AI-assisted workflows with your existing engineers — so the speedup outlives my engagement.

Currently available for freelance & consulting

Let’s scope it together

Skills

Deep on Apple. Fluent on Android.

A core skill set built over a decade of shipping — weighted toward Swift and SwiftUI, balanced by Kotlin, React Native and the engineering habits that make teams fast.

Apple platforms

iOS · iPadOS · watchOS · macOS

  • Swift
  • SwiftUI
  • UIKit & Auto Layout
  • Combine
  • The Composable Architecture
  • XCTest / Swift Testing
  • CoreData & SwiftData
  • AVFoundation & HLS
  • Xcode Cloud

Android

Kotlin-first, Compose-ready

  • Kotlin
  • Android Development
  • Jetpack Compose
  • Kotlin Multiplatform
  • Gradle & Play Console

Cross-platform

When one codebase is the right call

  • JavaScript / TypeScript
  • React Native
  • Redux & Redux-Saga
  • React Query
  • Jest
  • Native Modules (Swift ↔ RN)

Engineering craft

How the work gets shipped

  • Clean Code & SOLID
  • Unidirectional Data Flow (TCA, Redux)
  • CI/CD (GitHub Actions, Bitrise, Fastlane)
  • TDD / BDD
  • Git & code review culture
  • Analytics & observability
  • Accessibility (VoiceOver, TalkBack)
  • AI-assisted workflows (Claude Code, Cursor, Copilot, Antigravity)

Work

Selected projects, open on GitHub.

Personal products, frameworks and tools I build in the open. Some are shipping, some are still becoming — all of them are how I sharpen the craft.

All repositories

Client & freelance builds

  • GMVReact Native · TypeScript · MapTiler · Google Maps · Fabric
  • SoundsTrueReact Native · Native Modules · Swift · AVFoundation · HLS
  • CNCSwift · SwiftUI · TCA · Combine · CoreData · Bitrise
  • GloSwiftUI · TCA · HLS · Branch · GitHub Actions
  • VeryReact Native · Redux-Saga · GraphQL · Apollo

Experience

A decade of shipping for teams you already know.

Companies & clients I've built for

  • Starbucks
  • Paramount
  • Disney
  • ESPN
  • Citibank
  • One Medical
  • Butterfly Network
  • EPAM
  • Gorilla Logic
  • Globant
  • Rappi
  • Kiwibot
  • Making Sense
  1. 2024 — 2026Medellín, Colombia

    Lead Mobile Engineer at EPAM

    for Starbucks

    • Designed and delivered new features for the Starbucks US app using VIPER — robust, testable modules at massive scale.
    • Introduced AI-enhanced developer workflows to automate boilerplate and accelerate architectural scaffolding.
    • Drove accessibility compliance and expanded analytics instrumentation to sharpen product decisions.
    • Mentored engineers and set the bar for code review, testing and CI/CD.
    • Swift
    • VIPER
    • TCA
    • DI
    • Accessibility
  2. 2022 — 2024Medellín, Colombia

    Lead Mobile Engineer at Gorilla Logic

    for CBS / Paramount · Butterfly Network · One Medical by Amazon

    • Architected iOS features across multiple client products with Swift, SwiftUI, Combine, RxSwift and AVFoundation.
    • Led a scrum team on augmented-reality and troubleshooting features using Combine and TCA.
    • Kept feature parity with Android through tight cross-platform collaboration.
    • SwiftUI
    • Combine
    • TCA
    • CoreML
    • LaunchDarkly
    • Buildkite
  3. 2021 — 2022Remote

    Senior Mobile Developer at Making Sense

    for Lupl · Citibank

    • Built Swift/SwiftUI/Combine solutions for Lupl and native React Native modules for analytics and Apple Wallet.
    • Owned code signing and distribution for beta and production releases of Citibank's ShopYourWay Max.
    • Streamlined test automation, linting and builds with Firebase, GitHub and TestFlight.
    • Swift
    • SwiftUI
    • React Native
    • Apple Wallet
    • GitHub Actions
  4. 2019 — 2021Remote

    Lead Mobile Developer at Balance Consulting Group

    • Migrated a UIKit/OOP social app to functional-reactive Combine architecture backed by Firestore.
    • Architected an iOS/Android infant-monitoring wearable app in React Native with TDD, plus a Fitbit SDK watch face capturing 20+ hours of sensor data.
    • Evaluated Flutter vs. React Native and documented the trade-offs for the org.
    • Combine
    • Firestore
    • React Native
    • Fitbit SDK
    • Bitrise
  5. 2018 — 2019Medellín, Colombia

    Lead Mobile Engineer at Kiwibot

    • Built the Swift/UIKit iOS app for a robot-delivery service in Berkeley, CA — including real-time bot video via Tokbox.
    • Introduced MVVM + ReactiveCocoa and a server-driven Remote Dynamic Layout for the home screen.
    • Automated build and distribution with Fastlane.
    • Swift
    • UIKit
    • MVVM
    • ReactiveCocoa
    • Firebase
    • Fastlane
  6. 2016 — 2018Bogotá, Colombia

    Senior iOS Engineer at Globant

    for Disney · ESPN

    • Disney: ticketing and pass-management workflows — purchases, scheduling, renewals, payments — in a modular CocoaPods/Carthage architecture.
    • ESPN: server-driven dynamic UI, rich push notifications with media previews, and the progressive Objective-C → Swift migration.
    • Swift
    • UIKit
    • TDD
    • CircleCI
    • TeamCity
  7. 2016Bogotá, Colombia

    iOS Developer at Rappi

    • Re-architected the codebase to VIPER and hunted down memory leaks and retain cycles with Instruments.
    • Designed the real-time order-tracking UI reacting to push updates.
    • Swift
    • VIPER
    • Instruments
    • Auto Layout
  8. 2010 — 2015Colombia / Remote

    Skillet · PanamaCOM · Instartius at Earlier

    • HD recipe-video streaming for iPad (Skillet), B2B order management and cross-platform catalogs (PanamaCOM), and leading a small dev shop shipping web, WPF and mobile solutions (Instartius).
    • Objective-C
    • Xamarin
    • Android/Java
    • Node
    • Angular

Education

B.Sc. Software Engineering
Universidad de Ibagué · 2009 — 2013

Languages

Spanish Native · English Fluent · Japanese Beginner

Contact

Let’s build something worth opening twice.

Have a product, a team, or a problem worth talking about? Email me, or book a call directly — I read every message.

Email me Schedule a call
Message me on WhatsApp

me@zheref.io

Sergio Daniel L. García · Agentic Engineering

© 2026 zheref.io — Built with Gatsby & React. Palette inspired by Tanjiro’s flame 🔥 & haori 💚.