Pronounced: “YOO-zər ik-SPEER-ee-uhns” “YOO-zər in-tr-fays” “KROS FUNK-shuh-nuhl” “NEKST-jey-es” “ek-spow” “TUR-boh MOH-noh-REE-poh”
Role: Founding Full-Stack Product Engineer & Technical Architect
Delivered a robust, scalable, and cross-platform mobile application by architecting a modular monorepo using Turborepo, enabling seamless integration of an Expo React Native frontend, a NestJS backend API, and a shared component and utility layer powered by TypeScript, Tailwind CSS (via NativeWind), and Shadcn/ui. Leveraged PostgreSQL with Prisma ORM for reliable data persistence, integrated PostHog and GrowthBook to implement real-time A/B testing and feature flag experimentation, and established continuous integration and delivery pipelines through GitHub Actions and GitHub Pages for streamlined deployment. Designed the solution to align tightly with product goals and user experience standards by incorporating market research insights from Google Trends, Hotjar, and Mixpanel, which directly informed UI/UX decisions, onboarding flows, and content strategies. This implementation accelerated the delivery of a production-ready MVP within twelve weeks, improved developer velocity through clean architecture, and ensured ongoing performance optimization through observability tooling, modular testing, and real-time analytics.
UX/UI X-Functional NextJS Expo TurboMonoRepo
A robust, scalable cross-platform app with a NestJS backend, mobile front-end, and a modern Clean Architecture + monorepo setup utilizing Docker, PostgreSQL + Prisma, and Git / GitHub.
Table of Contents
| [Core | Monorepo Using Turbo + Package Manager](#core–monorepo-using-turbo–package-manager) |
| [Configure Back-End | PostgreSQL + Prisma](#configure-back-end–postgresql–prisma) |
| [Integration | Validation | Verification (IV&V)](#integration–validatation–verification-ivv) |
PUXUI-XFN/
├── apps/ # 💡 App-specific logic only
│ ├── mobile/ # 📱 Expo React Native App
│ ├── backend/ # 🔧 NestJS BFF/API
│ └── web/ # 🌐 Optional: Web app (Next.js admin)
│
├── packages/ # 📦 Shared across apps
│ ├── ui/ # 🎨 Reusable UI (NativeWind + Tailwind components)
│ ├── lib/ # ⚙️ Shared utils (analytics, hooks, feature flags)
│ ├── types/ # 🔤 Shared TypeScript types/interfaces
│ └── config/ # 🛠 ESLint, Prettier, TSConfig base
│
├── .github/workflows/ # 🚀 CI/CD
│ └── mobile.yml # Expo test/build pipeline
│
├── turbo.json # ⚡ Turborepo pipeline config
├── package.json
├── pnpm-workspace.yaml
└── tsconfig.base.json
GitHub
NPM
TurboRepo
Nest
# Create TurboRepo MonoRepo
npx create-turbo@latest myapp # Prompted to select Package Manager
cd myapp
pnpm install
# Create the apps directory (mobile, backend)
mkdir -p apps
cd apps
# Initialize Expo React Native App
npx create-expo-app mobile --template expo-template-blank-typescript
# Initialize NestJS App for Backend API
cd apps && npx @nestjs/cli new backend
# When prompted, choose TypeScript + npm or pnpm
cd backend && pnpm install && cd ..
# (Optional) Add Web app (e.g. Next.js dashboard)
npx create-next-app web --typescript
cd web && pnpm install && cd ..
cd ..
# Create shared packages
mkdir -p packages/{ui,lib,types,config}
touch packages/ui/index.tsx
touch packages/lib/analytics.ts
touch packages/types/index.ts
touch packages/config/{eslint.config.js,prettier.config.js,tsconfig.json}
# Init Git and pnpm workspaces
git init
pnpm install
cd apps/backend
pnpm add @prisma/client
pnpm add -D prisma tsx
npx prisma init
This creates prisma/schema.prisma and a .env file.
Create and Configure Your Database
uxuixfnjapp_dev) and user with a secure password.apps/backend/.env:
DATABASE_URL="postgresql://<username>:<password>@localhost:5432/<database>?schema=public"
prisma/schema.prisma to define your models (User, Post, etc.).pnpm run db:generate
pnpm run db:migrate
This applies your schema to the database.
pnpm run db:seed
PrismaService in your modules/services.
# Start PostgreSQL Server with Docker
# docker run --name pgdb -e POSTGRES_PASSWORD=mypassword -p 5432:5432 -d postgres
psql -h localhost -U postgres
# Create PostgreSQL Database and User
psql -U postgres
# Run In PSQL Prompt
CREATE DATABASE uxuixfnjapp_dev;
CREATE USER myuser WITH PASSWORD 'mypassword';
GRANT ALL PRIVILEGES ON DATABASE uxuixfnjapp_dev TO myuser;
Set Environment Variables (Edit .env)
DATABASE_URL="postgresql://myuser:mypassword@localhost:5432/uxuixfnjapp_dev"
DIRECT_URL="${DATABASE_URL}"
# Generate Prisma Client
pnpm run db:generate
# (Optional) Seed the Database
pnpm run db:seed
# Start the NestJS Backend
pnpm start:dev
Verify & Validate Configuration By:
If pnpm run db:migrate and pnpm run db:generate complete without errors the DB + Prisma are configured
If pnpm start:dev starts the server and you see a “Nest application successfully started” message, your backend is running.
(Optional) Visit your health endpoint (e.g., http://localhost:3001/health) or check the logs for successful startup
This is a TypeScript-based, modular monorepo mobile app project like yours—built with Expo (React Native), NestJS, and supporting clean architecture, feature flags, and A/B testing—here is a detailed implementation plan for the Syntax / Compile / Test-Driven Development (TDD) phase, aligned with best practices and DevOps readiness.
🎯 Goal of This Phase Ensure that:
Syntax is enforced and auto-correctable
Compilation never breaks CI
Code is modular, typed, and testable
Tests are written before or alongside features (TDD)
Tools provide immediate developer feedback on commit, push, or PR
Ensure each app and package has its own tsconfig.json, and that they extend from a shared base:
// tsconfig.base.json (in root)
{
"compilerOptions": {
"strict": true,
"target": "ES2021",
"moduleResolution": "Node",
"baseUrl": ".",
"paths": {
"@myapp/*": ["packages/*"]
}
}
}
Add
tsconfig.jsoninapps/mobile,apps/backend, and eachpackages/*, extending fromtsconfig.base.json.
| Layer | Tool | Description |
|---|---|---|
| Mobile (Expo) | Jest + react-native-testing-library | Unit & component tests |
| Backend (NestJS) | Jest + @nestjs/testing | Service & controller tests |
| Shared Packages | Jest | Test pure functions and utilities |
| E2E | Detox (mobile) or Playwright (web) | Optional full integration tests |
In root (shared tooling):
pnpm add -D jest ts-jest @types/jest
pnpm add -D eslint prettier lint-staged husky
Mobile-specific:
cd apps/mobile
pnpm add -D @testing-library/react-native jest-expo
Backend-specific:
cd apps/backend
pnpm add -D @nestjs/testing supertest
Eslint & Prettier Config in packages/config/
// packages/config/eslint.config.js
module.exports = {
extends: ['eslint:recommended', 'plugin:@typescript-eslint/recommended'],
parser: '@typescript-eslint/parser',
plugins: ['@typescript-eslint'],
rules: {
'no-unused-vars': 'warn',
'@typescript-eslint/no-explicit-any': 'warn'
}
}
// packages/config/prettier.config.js
module.exports = {
semi: false,
singleQuote: true,
trailingComma: 'es5'
}
Then in each app/package:
// .eslintrc.js
module.exports = require('../../packages/config/eslint.config.js');
🧪 Write a failing test (in __tests__ or *.test.ts[x])
Test UI components (React Native Testing Library)
Test business logic in services (NestJS or shared lib)
Mock dependencies
🧱 Implement just enough code to pass the test
Scaffold interfaces, service, or component
Keep it minimal and isolated
🛠 Refactor
Simplify
Reuse types from packages/types
Add edge-case tests
🧹 Lint & Format
pnpm lint → fix violations
pnpm format or prettier –write .
🔁 Re-run tests
In root package.json, add:
{
"scripts": {
"lint": "eslint . --ext .ts,.tsx",
"format": "prettier --write .",
"typecheck": "tsc --noEmit",
"test": "turbo run test",
"build": "turbo run build"
}
}
In apps/mobile/package.json:
{
"scripts": {
"test": "jest",
"lint": "eslint src --ext .ts,.tsx"
}
}
npx husky-init && pnpm install
// .lintstagedrc.json
{
"*.{ts,tsx}": ["eslint --fix", "prettier --write"]
}
# .github/workflows/ci.yml
name: CI
on:
push:
branches: [main]
pull_request:
jobs:
build-and-test:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v3
- uses: pnpm/action-setup@v2
with:
version: 8
- run: pnpm install
- run: pnpm lint
- run: pnpm typecheck
- run: pnpm test
| ✅ Artifact | Outcome of This Phase |
Type-safe builds via TypeScript
Syntax integrity via ESLint & Prettier
Confidence through testing via TDD
Reliable CI via GitHub Actions
A modular, scalable codebase ready for continuous integration and delivery
Implementation high-level overview of best practices for running tests, debugging, and managing integration, validation, and verification for your cross-platform monorepo mobile app project built with Expo + NestJS + Clean Architecture + Feature Flags:
| Type | Layer | Purpose |
|---|---|---|
| Unit Tests | Components, Services | Validate individual units (pure logic, UI, services) |
| Integration Tests | APIs, DB, Modules | Ensure systems/modules work together (e.g., controllers + services + DB) |
| E2E Tests | Full App Flow | Simulate real user behavior or workflows |
| Contract Tests | APIs/SDKs | Validate agreements between front-end and backend |
| Smoke Tests | CI/CD Environments | Lightweight high-level checks after deploy |
✅ Use test-driven development (TDD) where possible: write tests before implementing features.
✅ Co-locate tests near the code (componentName.test.tsx).
✅ Use mocks and stubs to isolate logic.
✅ Keep unit tests pure (no DB, no API).
✅ Snapshot only static visual components (not dynamic UIs).
✅ Don’t over-test 3rd-party libraries.
✅ Don’t use console.log for testing; use assertions.
✅ Avoid brittle tests that rely on specific data unless it’s locked down with mocks or fixtures.
🔍 Use Expo Debugger / React DevTools for component-level issues.
🧪 Add console.log, Reactotron, or use Flipper for deeper inspection.
🛑 Catch boundary issues using Error Boundaries and LogBox.ignoreLogs() selectively.
✅ Use jest –watch with breakpoints or debugger statements for test debugging.
✅ Use VS Code Debug Configuration for attaching to backend dev server.
🧩 Enable verbose logs in main.ts and use Logger.debug().
🐞 Use –inspect or –inspect-brk with node to attach a debugger.
The quality gate system at every layer.
✅ Use NestJS integration tests (e.g., spin up in-memory database + test API routes)
✅ Use tools like Supertest to validate HTTP requests.
✅ Front-end: Validate that components call the right APIs with mocked responses.
✅ Shared packages: Import and test across apps (mobile/backend).
Example:
describe('AuthController (e2e)', () => {
it('should register a user', async () => {
return request(app.getHttpServer())
.post('/auth/register')
.send({ email: 'test@test.com', password: 'pass123' })
.expect(201)
})
})
✅ Use Joi, Zod, or class-validator to validate input schemas (DTOs).
✅ Use feature flag validation (e.g., ensure EXPERIMENT_X routes or buttons are gated).
✅ Use Jest to validate logic against the original product spec or test cases.
Example:
expect(calculateSubscriptionPrice('annual')).toEqual(99.99)
✅ Code coverage reports via jest –coverage
✅ Pre-merge tests in CI/CD using GitHub Actions
✅ Manual verification via test scripts or QA
✅ Smoke test post-deploy (health check, versioning endpoint, feature toggles work)
Ensure every PR runs:
| Stage | Command |
|---|---|
| Linting | pnpm lint |
| Type Checking | pnpm typecheck |
| Unit Tests | pnpm test |
| E2E/Smoke | detox, playwright, etc. |
Use GitHub Actions or another CI to auto-reject PRs that fail any of the above.
🧪 Use .env.test config for predictable test behavior
✅ Use mock services (email, Stripe, notifications)
🧼 Reset DB state between tests
🧰 Maintain test data factories using libraries like faker or test-data-bot
| Practice | Why It Matters |
|---|---|
| TDD with lint/type check | Catches issues before runtime |
| Component + service mocking | Allows isolated, fast tests |
| Integration + E2E tests | Ensures modules work together |
| Feature flag & input validation | Ensures safety in experimentation |
| CI pipelines | Prevents regressions before merge/deploy |
| Dev tooling for debugging | Shortens feedback loop and increases productivity |