How Real-Time Appointment Availability Works

Real-time availability ensures customers see accurate open times.

The Challenge

Calendars change constantly:

• New appointments

• Cancellations

• External bookings

• Schedule changes

Static availability becomes stale.

Real-Time Approach

Query the calendar when the customer needs to see times.

Customer selects date
  ↓
Frontend requests availability
  ↓
Backend queries calendar API
  ↓
Calendar returns busy times
  ↓
Backend calculates free slots
  ↓
Frontend displays options

Calculating Free Slots

Given:

• Business hours

• Existing appointments

• Buffer times

• Appointment duration

Calculate available windows.

Caching Considerations

Some caching may be appropriate:

• Short TTL (seconds to minutes)

• Invalidate on booking

• Balance freshness vs. API calls

Race Conditions

Two people might select the same slot.

Handle this:
1. Validate before booking
2. If taken, show new availability
3. Let customer select again

Bookux

Bookux builds booking systems with real-time availability that stays accurate.

Related: How Appointment Scheduling APIs Work · Clickable Appointment Time Slots