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Juan H.

Juan H.

Senior Android & KMP Engineer | Performance & Architecture Specialist

Senior Android Engineer with over 14 years of professional experience specializing in high-performance mobile systems, scalable Kotlin Multiplatform (KMP) architectures, and complex SDK development. I excel at dropping into established codebases to untangle legacy dependencies, optimize system performance, and deliver robust, production-ready features. Most recently, I worked as a Senior Consultant for SmartThings, where I designed and optimized core features for the MOBI SmartKit SDK. I specialize in IoT-driven mobile experiences where efficiency, low-latency parsing, and solid architecture are absolutely critical. Beyond product engineering, I have a deep passion for compiler-level optimizations, KSP/KSP2, and low-level performance tuning. I am the creator of Ghost Serializer, an open-source, byte-first JSON serialization engine built for Kotlin Multiplatform that drastically reduces heap memory allocations by over 50% and speeds up API throughput by up to 66%. I bring this exact compiler-level understanding of the Android platform to every project I take on. How I can help your project: Complex Legacy Migrations: Upgrading older Android SDKs, libraries, and codebases safely without breaking production. SDK & Library Development: Building highly optimized, developer-friendly tools and libraries for internal or public use. Extreme Performance Tuning: Debugging memory leaks, reducing Garbage Collection (GC) overhead, and optimizing network/serialization layers. Kotlin Multiplatform (KMP): Architecting cross-platform data and domain layers to share business logic seamlessly between Android, iOS, and backends. Third-Party Integrations: Implementing complex, state-heavy SDKs (e.g., IoT protocols, WalletConnect/Web3, secure payment gateways). Core Tech Stack: Mobile: Android SDK, Kotlin, Java, Coroutines, Jetpack, KMP Architecture & Performance: KSP2, Memory Optimization, Bytecode-level tuning Backend & Tooling: Spring Boot, Ktor, Git, CI/CD Whether you need to architect a new mobile application from the ground up, scale an existing platform, or squeeze maximum performance out of a critical data path, I bring the technical vision and hands-on expertise to deliver exceptional results. Let's build something incredibly fast and reliable.

🇸🇻San Salvador, El Salvador$45/hr85% JSSSince Jul 2021

Earnings and projects

MRR
$6.9k

Last 6 months ÷ 6

World#2,914 / 412k
🇸🇻Country#3 / 839
Revenue, last 30 days
$6.7k

Last 6 months: $41k

World#3,308 / 412k
🇸🇻Country#4 / 839
Total earnings
$392k

Billed in all: $431k

World#4,617 / 412k
🇸🇻Country#5 / 839
Per project
$30k

$14k in the last 6 months

World#2,853 / 412k
🇸🇻Country#14 / 839
Projects, last 6 months
3
0% fixed100% hourly
World#66,482 / 412k
🇸🇻Country#50 / 839
Projects in all
13

Across 18 contracts

6% fixed94% hourly
World#175,714 / 412k
🇸🇻Country#138 / 839

Earnings, last 30 days

$431k+$6.7k earned in the last 30 daysBilled in all, before Upwork's fee · drag across the chart to see what was earned in any stretch
$420k$425k$430k$435kOct 9Oct 24Nov 8

Skill rankings: #1 in 1 skill of 9

Rarest: top 0.75% in Android SDK, of 805. Ranked by MRR among everyone on Upwork with the skill.

  1. 1Dependency Injection Framework36 freelancers · 🇸🇻 #1Top 3%
  2. 2Edge Computing28 freelancers · 🇸🇻 #1Top 7%
  3. 3SDK50 freelancers · 🇸🇻 #1Top 6%
  4. #6Android SDK805 freelancers · 🇸🇻 #1Top 0.75%
  5. #32Software Architecture964 freelancers · 🇸🇻 #1Top 3%
  6. #40Kotlin3,021 freelancers · 🇸🇻 #1Top 1%
  7. #66Android4,975 freelancers · 🇸🇻 #1Top 1%
  8. #67Git5,766 freelancers · 🇸🇻 #1Top 1%