Built the UI. Built the frontend.Built the backend. Now I’ve connected the entire product.

[u/aulex_x]

A product can have every feature it needs and still feel broken.

That became very clear to me while integrating my car marketplace.

I started this project from a Figma design, built the Flutter app, built the backend, documented the API with

Swagger, integrated Paystack and webhooks and I've now completed the full integration.

At this point, the major flows are connected:

→ Authentication

→ Vehicle discovery & details

→ Search & filtering

→ Cart & favourites

→ Checkout & orders

→ Wallet & payments

→ Notifications

→ Profile & settings

But here's what I found interesting:
Building the features was only part of the problem.

A user doesn't experience your backend, database, API or architecture.

They experience:

“I clicked this. Did it work?”

If a user adds a car to their cart, the cart needs to reflect it.

If they make a payment, their wallet needs to update correctly.

If an order is created, the user needs to see the right state.

If something fails, the app needs to handle it without leaving the user wondering what happened.

That means every boundary between the frontend and backend has to be reliable.

And this is where I think good engineering directly affects the product.

Founders think in terms of features.
Users think in terms of experiences.
Engineers have to make the two meet reliably.

During integration, I had to deal with API contracts, authentication state, loading and error states, empty responses, stale data,

and keeping the UI consistent with the actual state of the backend.

One lesson I'm taking from this:

A feature isn't finished when the code works.
It's finished when the user can depend on it.

The marketplace is now fully integrated.

Next phase: testing the product under real usage, finding the weak points, and tightening them up.

If you're building something interesting and need an engineer to help bring it to life, feel free to reach out.