Real-Time Appointment Booking System

A concurrency-safe reservation platform that completely eliminates double bookings during high-traffic registration windows using distributed mutex locking.

import Redlock from "redlock";
import { redisClient } from "./redis";

const redlock = new Redlock([redisClient], {
  retryCount: 5,
  retryDelay: 150,
});

export async function reserveTimeSlot(slotId: string, customerId: string) {
  const resourceKey = `locks:slot:${slotId}`;
  const lock = await redlock.acquire([resourceKey], 4000);

  try {
    return await executeSlotBookingTransaction(slotId, customerId);
  } finally {
    await lock.release();
  }
}