When we talk about habit trackers, most people imagine a simple checklist.

But turning that into a real, scalable full-stack app is a perfect playground for performance, data modeling, and clear architecture.

Over the next 20 days, I'm sharing every step of building a Habit Tracker with:

• Next.js for the frontend (fast, SEO-friendly React framework)


• Fastify for a high-performance Node.js API


• MongoDB + Mongoose for flexible, schema-driven storage

This post documents Stage 1 - Planning & Data Design, the foundation that sets the tone for the whole project.

Defining the MVP

My goal is a lean first release that's still valuable:

1. Create & edit habits - simple CRUD with validation


2. Daily logging - mark each habit as done/not-done per day


3. Weekly & monthly summaries - quick analytics for motivation

Staying focused here keeps scope tight and shipping fast.

Choosing the Stack

• Next.js: server-side rendering and API routes for snappy UX


• Fastify: modern, lightweight, and faster than Express


• MongoDB/Mongoose: flexible schema with room for growth

I debated Express vs. Fastify for a while; Fastify's plugin ecosystem and performance won.

Data Modeling

Three main collections emerged:

• User: auth info and settings


• Habit: name, description, schedule


• DailyLog: user-habit-date relationship + status

Indexes were planned early for quick weekly/monthly queries.

Lessons Learned

• Plan indexes first: analytics speed depends on it.


• Keep MVP honest: say "no" to nice-to-have features until the core is proven.

Open Source & Collaboration

The entire codebase and documentation are public:

👉 GitHub Repo

I'll push updates daily as I tackle UI, API endpoints, testing, and deployment.

Pull requests, issues, or architectural discussions are welcome.

Let's Connect

I'm sharing daily reflections, code snippets, and behind-the-scenes challenges on LinkedIn.

If you'd like to follow the journey, swap ideas, or collaborate on similar projects, join me there:

👉 [linkedin.com/in/ariansj(https://www.linkedin.com/in/ariansj/)

FullStack #NextJS #Fastify #MongoDB #OpenSource #WebDevelopment #HabitTracker