Josie Nelder

All work

Ember

An AI relationship coach for couples. I work on the React Native app, the Next.js website and the backend API.

Role
Senior Software Engineer
Team
Small team
Years
2025–present
Status
Shipped
Disciplines
  • Web
  • API
  • Payments
  • AI
  • Design system
  • Mobile

Ember is a relationship app for couples, built around Em, its AI relationship coach. It has had 35,000+ sign-ups.

I'm the primary mobile and front-end web engineer in a small team. I work on the React Native app and the Next.js website, and contribute to the backend API.

  • App Store image headed “Something to do together, tonight”: Ember’s home screen greets Jess and invites her to hold fingerprints with Phil to begin a Moment together.
  • App Store image headed “Meet Em. She gets relationships”: a discovery chat screen with Em, shown as a glowing orange face, offering to talk things through on your own or together.
  • App Store image headed “Insights you wouldn’t get on your own”: an insight titled “Balancing Time Together and Apart”, with a card saying an insight from Em is ready.
From the App Store listing.

AI features

Em's real-time voice sessions, built on ElevenLabs and LiveKit, have been used more than 25,000 times.

I've contributed to the backend behind Em, and worked with the team on a WhatsApp integration that brings Em's suggestions back into the app.

Website and invite links

I rebuilt Ember's marketing website from scratch in Next.js and TypeScript on Cloudflare Workers, replacing the old Webflow site.

It has CI with linting, type checks and tests, a blog with structured data, a sitemap, an RSS feed and consent-gated analytics.

Partner invite links used to be around 1,000 characters long. I wrote a Cloudflare Worker that turns short, branded links into AppsFlyer links and serves the iOS and Android app-link files.

Payments and backend

I contributed tested endpoints to the Postgres-backed API: server-side paywall rules, a Paddle subscription-management endpoint, and real-time WebSocket notifications from background jobs.

I also rebuilt the app's subscription paywall on Adapty, for the App Store and Google Play.

Design system and quality

I built the app's component library from the designer's Figma design system, now 230+ components, and set up a Storybook site for it. AI coding agents sped up the work.

I wrote 20 architecture decision records and a 75-term domain glossary. I grew the mobile test suite from zero to 2,600+ Jest tests using test-driven development.

Releases and integrations

The app ships to the App Store and Google Play, with Expo over-the-air updates between store releases. I helped implement the over-the-air updates.

I also helped set up the app's integrations: authentication (Ory, Apple and Google sign-in), analytics and attribution (Mixpanel, AppsFlyer) and crash monitoring (Sentry).