Built with Nexus

SlotBook: a complete booking app from one plan

We gave Nexus one description: an appointment-booking app for salons, tutors and clinics. Here is how the build went, step by step, with the real screens.

227automated tests passing

1 of 20simultaneous bookings for one slot accepted

~1.5 hoursof agent time

$13.21of AI model usage

Internal test, October 2026.

Step 1 · Plan

Three questions, then a plan

In Plan mode Nexus checked what the workspace offered, then asked three questions: which database to use, how to send emails, and which tech stack to pick. It wrote a detailed plan covering the data model, the availability engine, the double-booking guarantee and more than 60 tests.

Plan mode with clarifying questions and the written plan

The editor showing the bookings service and the agent summary

Step 2 · Build

A database, real code and tests

Nexus created a dedicated Postgres database, then built accounts and roles, business setup, a time-zone-aware availability engine, the public booking page, a dashboard, API keys and signed webhooks. Postgres itself rejects overlapping bookings: in a live test, 20 simultaneous requests for one slot produced exactly one booking.

Step 3 · Prove

Checked in a real browser, reviewed, fixed

Nexus ran the full suite (227 tests), then went through sign-up, setup, booking, rescheduling, cancelling, password reset and the staff view in a real browser, on desktop and mobile. A second agent reviewed the code and found real issues, including a debug page that would have been public in production. Nexus fixed every one and tested the fixes.