3R
Barber

The Challenge

There is no shortage of off-the-shelf booking systems on the market — the problem is they all charge monthly subscriptions. I needed to deliver public booking, real-time queue management, and metrics dashboards with zero infrastructure cost, while ensuring accurate timezone handling across regions and strictly isolating access by role:

• / Accurately converting BRT operating hours to UTC timestamps when generating booking slots.
• / Supporting 'any barber' appointments, where the first available barber claims the client, without concurrency conflicts.
• / Isolating data by role (client/barber/admin), ensuring barbers can only access their own queue and calendar.
• / Preventing duplicate bookings from form resubmissions (double-clicks, network retries) without requiring client accounts.

The Solution

The API runs on Hono in Cloudflare Workers, with Drizzle on D1 and all mutations validated via Zod. Authentication and RBAC are handled by Better Auth. Every barber route first retrieves the barber record based on the authenticated user — preventing one barber from accessing another's schedule. BRT→UTC conversion is centralized in a backend helper. Duplicate bookings (double-clicks, network retries) are blocked at the application level and reinforced by a unique index in the database.

// Slot generation: BRT hora + 3 = UTC hora
const BRT_TO_UTC_H = 3;

export function getDayBounds(dateBRT: string) {
  const [y, m, d] = dateBRT.split("-").map(Number);
  const startTs = Date.UTC(y, m - 1, d, BRT_TO_UTC_H, 0) / 1000;
  const endTs = startTs + 24 * 60 * 60 - 1;
  return { startTs, endTs };
}