Joseph Mattiello
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17+ years in the trenches

Joseph Mattiello is a New York-based engineering leader and mobile architect with 17+ years of iOS experience, currently on Wayfair's App Infrastructure team. He created Provenance EMU — the most popular open-source multi-system emulator for iOS (6.3k stars, 388k+ downloads, App Store) — holds 3 US patents from Sense Networks, and architects production AI tooling using Claude, Cursor, and custom MCP servers.

I started writing iOS apps before Apple released the SDK, hacking together Objective-C on jailbroken hardware. Since then I've led platform teams at Wayfair, NewsCorp (Director, iOS Platform — 8 regions), Cameo, and Hearst, working at every layer from kernel drivers to SwiftUI.


Outside of work, I maintain several high-profile open source projects (29k+ combined GitHub stars), build emulators that run on Apple Silicon without JIT, and write hardware drivers that ship in RetroArch's mainline iOS/macOS builds. I use AI tooling heavily — see the case study on the 3-agent CI orchestration I built across the Provenance org.

17+
Years in iOS
29k+
GitHub stars (maintained)
3
US Patents
4.4k
Contributions / year

What I build

Emulators, platform SDKs, hardware drivers, enterprise apps. If it runs on Apple hardware, I've probably built something like it.

Maintainer

Virtual Jaguar (libretro)

Admin and maintainer. Delivering the first open-source Atari Jaguar CD emulation (only other implementation is MiSTer FPGA). Extensive accuracy and performance fixes. AI-assisted development with A/B image regression testing. Powers Jaguar emulation in both RetroArch and Provenance.

Maintainer

Jaguar 240p Test Suite

Display calibration and video output verification for Atari Jaguar hardware. Feature completeness, automated releases, screenshot A/B regression testing via GitHub Actions.

iCube
Coming soon

iCube

GameCube & Wii emulator for iOS and tvOS. JIT-less Dolphin fork with optimized CPU/GPU interpreter code purpose-built for Apple Silicon. Metal shaders.

iFly
Coming soon

iFly

Dreamcast emulator for iOS and tvOS. JIT-less GPU/CPU interpreter optimized for Apple Silicon. Metal shaders, MFi controller support, save states, automatic cheat downloads.


Where I've moved the needle

Selected work where leadership decisions, technical depth, or both translated into measurable business outcomes. Numbers below are real or directly observable; story expanded on request.

Wayfair · L4 Mobile Engineer, App Infrastructure · 2025–Present
Performance Cost Optimization Observability

~$300k/year in bandwidth savings from two days of work.

Joined the App Infrastructure team supporting 60+ mobile engineers. Within the first months: shipped a video compression and caching strategy that pays for the team several times over, plus SwiftUI hot-path optimization and Datadog-instrumented bootup tracking.

The challenge

Video assets across product surfaces were being delivered with no shared compression or caching strategy. At Wayfair's scale, bandwidth costs grow fast — and the cost was hidden across teams, so no one owned it.

What I did
  • MP4 pipeline rewrite. Profiled the existing video delivery path, designed a re-encoding + caching strategy, and validated the savings against real production traffic via Datadog RUM.
  • SwiftUI purchase flow profiling. Instrumented the highest-revenue purchasing flow, identified rendering hot paths, and shipped targeted SwiftUI optimizations.
  • Bootup performance instrumentation. Stood up Datadog RUM tracking for cold-start, splash-to-interactive, and warm-resume timings — the data that's now driving the next wave of perf work.
  • AI tooling for the platform team. Built custom MCP servers, Claude skills/plugins, and n8n workflows that integrate with Jira and GitHub to automate cross-team engineering tasks.
Outcome

Roughly $300k/year in recurring bandwidth savings from the video work, real bootup metrics now feeding a structured optimization roadmap, and a growing internal AI tooling surface used across teams.

Stack Swift SwiftUI AVFoundation Datadog RUM CDN / Caching MCP / Claude n8n
NewsCorp · Director, iOS Platform · 2019–2020
Leadership Platform SDK Global Team DevOps

Inherited an iOS org trailing Android. A year later, we'd passed them on every metric that mattered.

Director of iOS Platform across NewsCorp's global brands — Wall Street Journal, NY Post, The Times UK, Knewz, and more — with engineering teams in NYC, London, Argentina, Ukraine, Russia, Hong Kong, Sydney, and Bangalore.

The challenge

iOS apps across NewsCorp's brand portfolio were lagging Android on app-store ratings, crash rates, performance, and bandwidth. Each brand was duplicating platform code. CI/CD was inconsistent. There was no shared iOS strategy.

What I did
  • Built a shared iOS Platform SDK as an "internal open source" model — every NewsCorp brand consumed it, contributed back, and got the next perf/stability fix for free.
  • Restructured and hired across 8 regions. Set up cross-region code review, release cadence, and on-call ownership.
  • Modernized CI/CD with GitHub Actions, automated PR management, and Jira integrations — the same DevOps automation patterns I'd later carry into my OSS work.
  • Shipped Knewz from scratch — NewsCorp's news-aggregation app — as a greenfield iOS project, end-to-end, while running platform.
Outcome

iOS surpassed Android across the board on stability, app-store ratings, performance, and bandwidth usage. The platform SDK was adopted by every brand and outlived my tenure. Knewz launched on iOS internally-built, on time.

Stack Swift Objective-C Platform SDK GitHub Actions Jira Automation Fastlane Distributed Teams
Cameo · Principal iOS Engineer · 2020–2021
React Native Native Bridging CI/CD AVFoundation

First native iOS dev on a React Native team — fixed the build, shipped HD video.

Cameo was scaling fast and the iOS build pipeline was cracking. I came in as their first dedicated native iOS engineer, with a mandate to make the engineering org actually able to ship — and to enable native-quality features the JS bridge couldn't deliver.

The challenge

The React Native iOS build was slow and flaky — both in CI and locally. Engineers had stopped trusting green builds. And video quality was capped by what JavaScript could push through the bridge.

What I did
  • Rebuilt the iOS RN build pipeline. Profiled every stage, eliminated flakiness sources, and parallelized where it mattered. CI went from "maybe" to predictable.
  • Shipped HD video as a native React Native module. Built compression, transcoding, and playback in Swift/AVFoundation, exposed via the React Native bridge — gave product the quality bar they couldn't get from JS.
  • AR filter exploration. Prototyped native AR filters using ARKit / Core Image, demonstrating the headroom available once you stop fighting the bridge.
  • CI/CD migration to streamline the team's release cycle.
Outcome

Predictable CI, HD video shipped natively, and a clear pattern for the team: when the JS bridge isn't enough, here's how we drop down to native. Engineering velocity recovered.

Stack Swift React Native AVFoundation ARKit RN Bridge CI/CD
Provenance + libretro + 240p Test Suite · Maintainer · 2024–Present
AI Engineering Multi-Agent CI DevOps Open Source

Three autonomous AI agents sharing one orchestration layer — built into production OSS pipelines.

A multi-agent CI ecosystem across the Provenance org and upstream libretro contributions. Claude, Cursor, and Kimi Code coexist as routable workers, with model auto-selection by code-pattern heuristics, fallback resilience, and a scheduled poller that bypasses GitHub's bot-actor approval gate.

The challenge

Maintaining a 13-year-old open-source project with 6.3k stars, 79 contributors, 388k+ downloads, and an active App Store presence — while working full-time. Solo-maintainer velocity is the rate-limiter. Generic "use Copilot" doesn't move the needle.

What I built
  • Reviewer-model auto-selection by static diff analysis. The PR review workflow grep's the diff for thread-safety patterns (Realm, @Model, actor, @MainActor) — simple PRs route to Claude Sonnet; thread-safety-sensitive PRs route to Claude Opus. Real cost optimization, not vibes.
  • Three agents, one action vocabulary. Claude Code, Cursor Agent, and Kimi Code share dispatch verbs — implement_issue, fix_ai_review, fix_rebase_conflict, ai_approved — routed by branch name and PR labels. Effectively a multi-agent orchestration layer on top of workflow_dispatch.
  • Kimi Code as Anthropic-API-compatible fallback. When Claude credits run low, the same Claude Code CLI binary redirects via ANTHROPIC_BASE_URL to drive Kimi — zero workflow rewrite.
  • Scheduled Copilot review poller. GitHub blocks event-triggered workflows from bot actors. The 10-minute cron poller bypasses the approval gate by running as a trusted scheduled actor — a deliberately documented workaround.
  • Auto-fix CI on the wiki repo. Spell-check / link-check failures spawn Claude via anthropics/claude-code-action, which fixes the root cause and opens its own PR (with Copilot reviewer auto-requested).
  • AI-driven localization. Diff-aware Claude Haiku pipeline translates only changed strings into 11 languages — cost-controlled by extracting just the new keys, not the whole file.
  • Repo health monitor. Cron job detects stuck PRs, re-dispatches reviews, and maintains a pinned automation-health issue.
  • Upstream-merged Claude Code workflow. Installed Claude Code into the libretro upstream itself (PR #107) — alongside 19 merged feature PRs covering save states, RetroAchievements, SIMD blitter, WASM/Emscripten, and Jaguar CD support.
Outcome

OSS velocity sustained at scale on a solo-maintainer schedule. The pipeline handles routine review, rebase conflicts, localization, and CI failures autonomously — escalating to me only when bounded review cycles complete or 3-cycle limits are hit. This is what "AI engineering leadership" looks like when it's real, not slideware.

Proof — read the code
Stack Claude Code Cursor Kimi Code Anthropic API GitHub Actions workflow_dispatch MCP

Where I've worked

From pre-SDK jailbreak apps to platform infrastructure serving millions of users.

Wayfair 2025 — Present
L4 Mobile Engineer — App Infrastructure
New York, NY (Remote)
  • Instrumented Datadog RUM across the iOS app, giving the team release-over-release UX metrics for the first time
  • Built Datadog dashboards used by multiple teams for performance triage and release validation
  • Created a bootup task profiling system that catches performance regressions before they ship
  • Developed AI-powered skills, MCP servers, and plugins adopted by internal engineering teams
  • Automated cross-team workflows with n8n, Jira, and GitHub integrations
Wayfair Jan 2025 — Sep 2025
L4 Mobile Engineer — Product Discovery
New York, NY (Remote)
  • Owned the product discovery feature set on iOS, driving measurable gains in engagement and conversion
  • Cut app startup time and reduced network overhead through targeted profiling
  • Redesigned the homepage layout with shimmer states and modern interaction patterns
Matti Media LLC 2021 — Present
Founder
New York, NY
  • Creator of Provenance, the most popular open-source multi-system emulator for iOS/tvOS/macOS. Now on the App Store (388k+ downloads, 6.3k stars)
  • Ported 50+ C/C++ emulator cores to Swift Package Manager, optimized for ARM
  • Full SwiftUI interface with Spotlight, QuickLook, FileProvider, Stickers, and Siri integration
Cameo 2020 — 2021
Principal iOS Engineer
New York, NY
  • First native iOS hire on a fully ReactNative codebase. Rebuilt performance-critical paths in Swift
  • Added HD async video compression, cutting bandwidth costs and upload times
  • Migrated CI/CD from shell scripts and CircleCI to GitHub Actions (10x faster PR validation)
NewsCorp Inc. 2019 — 2020
Director iOS Platform (Global HQ)
New York, NY
  • Ran iOS development across 8 regions. Built the core SDK used by DowJones, NYPost, The Australian, Barrons, Times UK
  • Hired and led the Knewz iOS team from zero. 4.5+ star rating, unsolicited App Store feature by Apple
  • Stood up a satellite team in Barcelona and restaffed engineering in Argentina, Bangalore, and Ukraine
Salido Inc. 2018 — 2019
Lead Developer
New York, NY
  • Ran the front-end team and led architecture for 3rd-party vendor integrations
  • Created the first Swift-native XML-SOAP framework with full Codable support
Hearst Digital News 2012 — 2018
Lead Mobile Architect / Team Lead
New York, NY
  • Took the app from constant crash reports to a 4+ star rating (80% crash reduction, 30% less memory)
  • Architected the universal app rewrite on Swift 2.0, CoreData, and CoreText
  • Set up Hadoop analytics systems and managed office and colo network infrastructure
Sooloos / Roonlabs 2010 — 2012
Software Engineer (iOS/macOS)
New York, NY
  • Bridged C#/Mono audio decoders to Core Audio. Wrote CoreMIDI and CoreAudio wrappers contributed to MonoMac
  • Sole Objective-C developer and UI designer for the Sooloos iOS sync and playback app
Sense Networks 2008 — 2010
Software Engineer (iOS/DevOps)
New York, NY
  • Built Citysense for iPhone before Apple released the SDK. Named inventor on 3 US patents. Company featured on the cover of Newsweek ("The Next Google")
  • Created CabSense, an NYC taxi availability app. Featured in the NY Times (3 articles), TechCrunch, VentureBeat, Wired UK, and more
  • Accepted as an official FSF/GNU developer through major GNUstep PBXBuild contributions
Earlier 2006 — 2007
People Security (Security Consultant) • AT&T Tech Channel (Producer)
New York, NY / Bedminster, NJ
  • People Security: Developed secure coding training with Dr. Hugh Thompson (buffer overflows, stack exploits)
  • AT&T: Booked and produced segments with Emanuel Goldstein (2600), Whit Diffie (RSA), Jack Dorsey (Twitter), H.D. Moore (Metasploit)

Technical expertise

⌨️ Languages

Swift5/5
Objective-C5/5
C++4/5
C5/5
JavaScript4/5
Python3/5
C#3/5

🔧 Tools & Platforms

AI/LLM Tooling5/5
GitHub Actions / CI/CD5/5
Datadog (RUM, APM)4/5
n8n Automation4/5
Jira Automation4/5

📱 SDKs & APIs

iOS/tvOS SDK5/5
UIKit5/5
SwiftUI5/5
Core Audio / MIDI5/5
XCTest5/5
AVFoundation4/5
Combine4/5
Realm5/5

Community contributions

I maintain libraries with tens of thousands of stars, write drivers for RetroArch, and contribute to projects I use every day.

RetroArch

Authored Apple platform drivers: camera (AVFoundation), microphone, CoreMIDI, and WiFi — all merged to mainline iOS/macOS/tvOS builds

UTM

Virtual machine host for iOS/macOS

Hero Transitions

Maintained custom view controller transition library for Swift

RxSwift Community

Maintainer of RxRealm & RxReachability

XMLCoder

Significant PRs — attributed intrinsic value coding, dynamic node encoding

Mono / Xamarin

Authored CoreMIDI, CoreAudio, and Foundation C# wrappers for MonoMac

GLideN64

Open-source N64 graphics plugin contributions

SideStore

21 merged PRs. Rust build integration, error handling, settings, pairing. Org member

mupen64plus

Buffer overflow fix in core, removed system() calls for iOS/tvOS compatibility

Flycast (Dreamcast)

Metal renderer fixes, Vulkan portability, audio drift fixes (4 open PRs)

View all on GitHub →

Patents, press & impact


Foundation

🎓

BS, Computer Science

University at Buffalo

2004 — 2008

Beyond code

When I'm not deep in Xcode or a debugger, I'm wrenching on my M2 CS or behind the decks.

🏎️

BMW M2 CS

6-speed manual, track days, and weekend wrenching. Documenting the build and drives on Instagram.

@m2_cs_6mt
🎧

Music & Production

DJ sets on SoundCloud. Build Max for Live patches and reverse-engineered USB/MIDI drivers for DJ controllers and synths.

joe-mattiello

Also a terminal app

This resume runs as a native Swift TUI application with ncurses. Tabs, search, scroll — all in your terminal.

joseph.mattiello.resume — zsh

Try it yourself:

git clone https://github.com/JoeMatt/joseph.mattiello.resume.git && cd joseph.mattiello.resume && swift run
ESC