Case study
Apexevo
A health app for iPhone and Android that brings nutrition, training, sleep and medication into one place, with safety screening before any guidance. In private beta.
Overview
Apexevo is a health app for iPhone and Android. One app covers what you eat, how you train, how you sleep and what you take, and the parts are built to talk to each other. It is in a private beta at apexevo.musmannaeem.com, opening to a small group first.
The user picks a goal, such as building muscle, losing weight or staying healthy overall, and onboarding gathers enough about their body, training, diet, sleep and medical history to tailor everything after it. From there the app sets calorie and protein targets and explains them, prescribes training for the equipment the user actually has, reminds them about medication and tracks adherence, and reviews the week across six areas of health.
What I own
The product and its roadmap, the design system, the mobile app, the admin panel, the marketing site, the backend rules and the release process.
Complexities tackled
One computation core that owns every number. Targets, the user’s rating, exercise selection, load progression, plateau detection and the safety limits all come from one core library, so no screen can show a number the core did not produce. Every recommendation is stored with the version of the core and a hash of its inputs, so it can be reproduced later.
Safety before advice. A health app that guides someone it should not is worse than no app. Screening runs before any guidance, and the safety limits are rules the rest of the app cannot cross.
Health maths that cannot mix units. Weights, energy and doses are typed by unit in the code, so passing pounds where kilograms are expected is a compile error rather than a quietly wrong number in someone’s plan.
An admin panel that cannot see health data. The exercise catalogue, seed foods, app configuration and support live in a separate Angular web app. Its privileges are scoped so an admin can never browse a user’s health data, and signing in to it needs an authenticator app.
Offline first, and free to run. The app works with no connection and syncs when it returns. Logs and daily summaries are written in the same Firestore transaction, so the summaries can never drift from the logs. It runs on Firebase’s free tier, with a Cloudflare Worker for the few things a phone must not be trusted to do, each request checked against the user’s Firebase token.
Where it started
Apexevo began in February 2026 as a habit tracker built as a role-playing game, in Flutter with Riverpod, Hive and Firebase. Daily consistency earned experience, and each area of life levelled up over months. In September 2026 it was rebuilt from scratch in React Native and Expo as a broader health app.
Stack
React Native with Expo and expo-router, TypeScript in strict mode, Firebase Authentication, Cloud Firestore, App Check and Remote Config, a Cloudflare Worker for server-side work, an Angular admin panel, and an Astro marketing site.
Working on something similar?
Tell me what you are building and what is in the way. I will tell you honestly whether I am the right person for it.