Jacob Relkin

$ about

# Hands-on, by choice.

            DoximityFlagship iOS ReleaseLed v5.0 for the network now used by 80% of U.S. physicians, and architected the SDK behind its partner medical schools’ branded apps.

            PinsAcquired by SquareBuilt Pins end-to-end. After the acquisition, joined Square’s Register Foundation team, which owns the core iOS infrastructure under Square Register.

            Breathometer$1M Shark Tank DealFounding iOS engineer for the consumer breathalyzer that took $1M from all five Sharks. Built the app and its Bluetooth and signal-processing stack.

            JSwipeAcquired by Spark NetworksBuilt the iOS app end-to-end for a dating product that grew past 450K users and was acquired by Spark Networks, the JDate owner.

Today I work with AI daily, Claude Code included, and build tools of my own on the Claude platform, several of them below. I also advise a venture-backed startup in fintech and applied AI.

$ projects

# Built on my own time, with AI in the loop.

Runout

web app

The edge for serious pool players: scout any opponent, know your odds before the break, and follow tournaments live.

Designed and shipped end to end: five live product surfaces (player intel, edge calculations, tournament data, a personal match journal and broadcast-quality share cards) in a production TypeScript monorepo on Vercel. The Next.js 16 app and a versioned site-generator package run on one shared analytics engine that models race odds, event EV and full standings reconstruction.

architecture

data: Its own private results store: every FargoRate-rated player’s entries and matches, deduplicated, with personal fields stripped before anything is saved.
ai: On-demand Claude scouting reports on any opponent, bring-your-own-key, cached until their rating moves.
proof: Accuracy you can audit: odds match FargoRate to five decimal places, a golden fixture pins the engine to the published player page’s own answers, and 17 real events replay on every run.
tests: Roughly 2,000 automated tests across Vitest, node:test and Puppeteer, on self-hosted Apple Silicon CI.

TypeScript · Next.js · Vercel · Claude API · Vitest · Puppeteer

See it live on its first player site, 75 tournaments deep: amateurcueist.me

Tzelem

iPhone · iPad · Mac · web

A private, self-hosted photo and video library.

architecture

server: Standard-library Python. Indexes media in place into a column-encrypted SQLite database.
access: Mutual TLS from its own certificate authority; devices enroll with a one-time QR link.
clients: A vanilla-JS web app and SwiftUI apps on one Swift 6 core package, kept in step by shared golden fixtures.
search: Optional CLIP search, run locally with ONNX: no cloud, no vector database.
tests: 7,000+ across Vitest, pytest and Swift Testing; TestFlight builds from CI.

Python · SQLite · Swift 6 · SwiftUI · ONNX Runtime

Pardes

iPhone · iPad · web

A source-based case for veganism in Jewish tradition.

architecture

site: Next.js App Router. Five chapters prerendered from a typed registry of 251 sources.
sources: Prose cites by id and the bibliography is generated from the same records. CI fails if a quotation drifts from its verified snapshot.
devices: A SwiftUI kit: an iPad stage driven by iPhone remotes over Multipeer Connectivity, on a versioned JSON protocol.
tests: 247 across Vitest and XCTest.

Next.js · TypeScript · MDX · SwiftUI · Multipeer Connectivity

Posty

web app

An editorial agent for X drafts.

architecture

shape: A React and Vite client over an Express API.
agents: Two Claude calls in parallel: Sonnet with server-side web search checks each claim and rewrites the post; Haiku reads tone, audience and risk.
resilience: Either call can fail without losing the other. Responses are cached by hash, and rate limits back off and retry.

React · Express · Claude Sonnet · Claude Haiku · web search

$ ls projects/ # 5 more

jacobrelkin.mesiteThis site: homepage, CV, and PDF rendered from one data file by a custom build. Claude Code in the loop, headless-Chrome tests on every change.
cuescopecomputer visionComputer-vision analysis of pool match video: every shot with its start and end, which game it belonged to, who won, and clip ranges ready to cut.
CodexBar SigmamacOS appA menu bar watchdog for Claude Code usage: reads CodexBar’s history, scores the burn rate against a median and MAD baseline, and notifies the moment it spikes.
ReclaimmacOS appWhere the disk space went, and how to get it back: treemap, size-versus-age chart, duplicate finder, build-cache cleanup. Everything goes to the Trash and can be undone.
TroveiPhone · iPad · MacSave anything from any app’s share sheet into one private, searchable library that syncs across iPhone, iPad, and Mac. In development.

$ experience

# A long-running independent practice, with in-house roles alongside.

Independent Practice

2013 – Present

Software Consultant & Technical Advisor

# Contract engineering and advisory work for startups and public companies

Embedded as a senior engineer across 15+ clients, shipping production iOS in fintech, healthcare, social, IoT, and AI. Engagements include ShopKeep, JSwipe, Amicus Therapeutics (NASDAQ: FOLD), and Screenshop.
Technical advisor to a venture-backed stealth startup in fintech and applied AI.

Bottleshake

2016 – 2017

Engineering Lead

# B2B marketplace connecting brands with influencers

Joined as engineering lead, building and managing a five-person cross-functional team that owned iOS, web, and the backend API.
Shipped Login with LinkedIn and a full UI/UX redesign, and rebuilt the match-scoring algorithm around weighted signals and deterministic ranking.

Square (now Block)

NYSE: XYZ

2013 – 2015

iOS Platform Engineer

# Core infrastructure behind Square Register, the flagship point-of-sale app

Joined through the acquisition of Pins, which I had built end-to-end, and was promoted to the Register Foundation team.
Cut CI build times by more than 30% with parallelized builds, test sharding, and caching. Prototyped Square Invoices at Hack Week.

Breathometer

Shark Tank

2013 – 2014

Founding iOS Engineer

# Consumer Bluetooth breathalyzer — $1M from all five Sharks on ABC’s Shark Tank, Season 5

Solo-built the application, the Core Bluetooth stack, and the real-time signal-processing pipeline that turned raw sensor data into BAC readings.
Built a transport-agnostic communication layer that routed I/O to whichever hardware was connected, Bluetooth or audio jack, behind a single interface.

Doximity

NYSE: DOCS

2011 – 2013

Lead iOS Engineer

# Professional network for U.S. physicians

Led v5.0, the platform release that brought Search, DocMail, DocFax, and physician forums to the iOS app.
Architected a white-label SDK deployed at Stanford, Harvard, Penn, UCSF, and UCSD, with per-institution theming, authentication, and data partitioning from a single codebase.
Built the iOS app for Amion, Doximity’s clinician scheduling platform: HIPAA-compliant messaging, on-call shift management, and offline-first sync for 200K+ providers across 350+ health systems.

Earlier Roles

2009 – 2011

Giftiki, Appcelerator, Freeverse

Giftiki (Lead iOS Engineer) — Built the social gifting app acquired by LaunchRock in 2012.
Appcelerator (iOS Platform Engineer) — One of four core engineers on Titanium Mobile; owned the Objective-C/JavaScript runtime bridge.
Freeverse (Software Engineer) — Shipped two commercial iOS game titles during the early iPhone OS era.

$ work

# 12 products, from hardware to healthcare.

Doximity

NYSE: DOCS

Lead iOS Engineer

The professional network for U.S. physicians, on iOS: search, secure messaging, fax, and forums, plus the white-label SDK that ran five medical schools’ branded apps from one codebase.

Obj-C · UIKit · Core Data · REST APIs · White-Label SDK

Amion

Doximity · NYSE: DOCS

Lead iOS Engineer · Doximity

Doximity’s clinician scheduling platform, used by 200K+ providers across 350+ health systems. Delivered HIPAA-compliant messaging, on-call shift management, and offline-first sync for clinicians on call.

Swift · UIKit · Offline Sync · Push Notifications · HIPAA

Breathometer

IoT / Hardware

Founding iOS Engineer

Consumer breathalyzer that turns a breath sample into a BAC reading on the phone. One codebase drove both hardware variants, Bluetooth and audio jack, through a transport-agnostic I/O layer.

Obj-C · Core Bluetooth · Audio I/O · Signal Processing · Hardware Integration

Square Register

NYSE: XYZ

iOS Platform Engineer

Square’s point-of-sale app. On the Register Foundation team, owned the platform layer every feature team built on: shared libraries, build tooling, and CI.

Obj-C · Swift · Jenkins CI · Modular Architecture · Internal Tools

ShopKeep POS

Acquired by Lightspeed

Senior iOS Engineer · contract

iPad point-of-sale for tens of thousands of small businesses. Built the offline-first transaction engine: durable local queuing, conflict-resilient sync, and deterministic recovery, so a sale completes even when the network doesn’t.

Swift · Core Data · Payment APIs · Offline Sync

Galafold® MyDay

NASDAQ: FOLD

Senior iOS Engineer · contract

Medication-adherence companion app for Amicus Therapeutics’ rare-disease therapy. Built to HIPAA and WCAG standards: dosing reminders, adherence tracking, HealthKit integration, and audit-logged patient interactions.

Swift · HealthKit · Local Notifications · Accessibility · HIPAA

$ ls work/ # 6 more

JSwipeAcquired by Spark NetworksSwipe-to-match dating app. Matching engine, WebSocket chat protocol, StoreKit purchase flow, and push-driven re-engagement, from launch through the 2015 acquisition.
ScreenshopVisual SearchVisual fashion search: snap an outfit, find shoppable matches. Built the whole iOS capture pipeline: permission-aware camera access, real-time capture UX with framing guides, and the results interface.
BottleshakeB2B PlatformBrand–influencer marketplace with real-time campaign matching. Owned the product across iOS, web, and the backend API as engineering lead.
GiftikiAcquired by LaunchRockSocial gifting app: friends pool money for one bigger gift. Built gift discovery, social-graph integration, and push-driven engagement flows. Featured in Apple’s “New & Noteworthy.”
PinsAcquired by SquareLocation-based social discovery. Built map clustering tuned for dense urban data, bidirectional Core Data sync with conflict resolution, and geofenced content delivery.
Titanium MobileAppceleratorAppcelerator’s open-source cross-platform mobile framework, behind thousands of production apps. One of four core engineers; owned the Objective-C/JavaScript bridge that exposes native iOS APIs to JavaScript and reconciles reference counting with its garbage collector.

$ skills

# What I’m good at, with the work that proves it.

Apple platform engineering

expert

The full Apple toolkit, UIKit through SwiftUI, and apps that keep working through new iOS releases and growing teams.

# proof: Doximity v5.0 · Square Register

Bluetooth & hardware

expert

Connecting iPhones to hardware: Bluetooth devices, audio-jack accessories, and live sensor data, behind one interface so the app never cares which it is talking to.

# proof: Breathometer

Offline-first data & sync

expert

Apps that keep working without a connection and sync correctly when it comes back.

# proof: ShopKeep POS · Pins · Amion

Platform & architecture

expert

The shared foundation a team builds on: modular code, clean APIs, white-label SDKs, and build pipelines that stay fast as the team grows.

# proof: Square Register Foundation · Doximity white-label SDK

Regulated product engineering

expert

Healthcare, pharma, and payments: HIPAA data handling, audit trails, and accessibility.

# proof: Amion · Galafold MyDay · ShopKeep POS

Testing & delivery

expert

Test-driven development with XCTest, XCUITest, and snapshot tests, shipped through GitHub Actions and Jenkins to TestFlight and the App Store.

# proof: Square Register CI · this site

Real-time & networking

advanced

APIs, live chat, push notifications, and in-app purchases: the plumbing between the app and everything else.

# proof: JSwipe · Bottleshake

AI in the workflow

advanced

Claude Code every day: AI agents that write and test code, language-model features inside apps, and prompts written with the same care as an API.

# proof: Runout · Posty · this site

Languages & runtimes

expert

Swift and Objective-C first; TypeScript, JavaScript, and Python when the product reaches beyond iOS.

# proof: Titanium Mobile · Stack Overflow

# Languages

Swift (expert)
Objective-C (expert)
TypeScript (advanced)
JavaScript (advanced)
Python (advanced)
Ruby (familiar)

# Architecture & data

MVVM (expert)
TCA (advanced)
Protocol-oriented design (expert)
Offline-first sync (expert)
Modular Swift packages (advanced)
Dependency injection (advanced)
State management (advanced)
REST (advanced)
WebSockets (advanced)
GraphQL (advanced)

# Apple frameworks

UIKit (expert)
SwiftUI (expert)
Core Bluetooth (expert)
Combine (expert)
Swift Concurrency (expert)
Core Data (advanced)
SwiftData (advanced)
MapKit (advanced)
Core Location (advanced)
HealthKit (advanced)
AVFoundation (advanced)
StoreKit (advanced)
Push Notifications (advanced)
Accessibility (advanced)

# Testing & delivery

Test-driven development (expert)
XCTest (expert)
XCUITest (expert)
Snapshot testing (expert)
Continuous integration (expert)
Continuous delivery (expert)
TestFlight (expert)
App Store Connect (advanced)
Instruments (expert)
Fastlane (familiar)
GitHub Actions (advanced)
Jenkins (advanced)
Swift Package Manager (advanced)

# AI

Claude Code (advanced)
LLM integration (advanced)
Prompt design (advanced)

# education & certifications

Lev Academic Center (Jerusalem College of Technology) · Computer Science

Newton Academy iOS Developer
Arc Certified Remote Developer

$ community

# Public work, with the numbers pulled live.

Contributing to the iOS and broader developer community: Stack Overflow answers that still surface in search years later, and core work on the open-source Titanium runtime bridge.

$ gh --user plantpurecode — lifetime contributions —
past 12 months10+
years active over a decade on GitHub

$ contact

Hiring, building, or advising?

If you think I could help, I’d love to hear about it.

$ colophon

# How this was built.

This page is its own work sample. Hand-built, with Claude Code in the loop. Here is the pipeline behind it, with the numbers taken from this build.

$ cat data.json
one source of truth
Every word on this site lives in a single 1067-line JSON file. Templates carry structure, never copy, so the CV, the PDF, and the homepage can never disagree.
$ node build.js
custom build, no framework
A 690-line build script with its own template engine renders 5 templates into static pages, prints the PDF, and screenshots the social image in headless Chrome. 0 runtime dependencies; 1 dev dependency.
$ npm test
tested in a real browser
115 test cases across 8 suites drive the built pages in headless Chrome: layout at phone and desktop widths, interactions, copy, the terminal, and the API handlers.
$ git push
every change gets a URL
GitHub Actions runs the suite on every pull request and deploys a preview. Nothing deploys without a green run.
$ gh release create
release-gated production
Production ships only when a GitHub release is published. Merging to main updates staging, not the live site.
$ curl /api/github
live where it matters
Two serverless proxies fetch GitHub and Stack Overflow numbers with caching and baked-in fallbacks.

# this build: 3a07aa7 · 2026-10-17

HTML, CSS, and JavaScript, no framework
one data file, custom build
tested in CI on every change
release-gated deploys
live GitHub and Stack Overflow via serverless proxies
view transitions from the homepage
works without JavaScript
honors reduced motion
print-ready
keyboard command palette

Flagship iOS Release

Acquired by Square

$1M Shark Tank Deal

Acquired by Spark Networks

# Languages

# Architecture & data

# Apple frameworks

# Testing & delivery

# AI

Hiring, building, or advising?

# senior and lead engineering roles

# embedded engagements

# technical advisory

one source of truth

custom build, no framework

tested in a real browser

every change gets a URL

release-gated production

live where it matters