Scaling Bookings for large demand
Published Jan 28 2021 02:26 PM 17.5K Views

Editor's note (2/3/22): Removed a broken link to UserVoice and fixed a link to our Bookings customer stories that was taking people to a third-party site.

Editor's note (1/28/21): Title was updated to make it shorter


There is a growing need for virtual meetings, consults, and appointments but also an increase in the amount of time people are dedicating to try to schedule those appointments. Back and forth phone calls, emails, text messages. Bookings can make it easier, so you can spend more time talking to customers rather than trying to schedule them, and it does it in a secure and integrated way with Microsoft 365.


Microsoft Bookings helps making scheduling and managing appointments easy and seamless. It does this through a web-based booking tool where people have the flexibility to see and book services when it’s convenient for them, it makes it easier to manage staff’s time by integrating with Outlook’s calendar and keeps everyone updated with timely and automatic email confirmations and reminders to reduce no-shows, all these also helps organizations reduce repetitive scheduling tasks.


Bookings is flexible, customizable, secure as it uses a mailbox in Exchange Online, and can be designed to fit scenarios and needs of different parts of an organization.


We have worked with various industries to enable different scenarios. Tele-Health by virtual consultations with doctors through Microsoft Teams, educational classrooms, financial consulting, organizations internal services like legal/IT/HR provided to their employees,  candidate interviews, assisted shopping in retail, and government services. To read more on how customers are using Bookings for these scenarios, please click here.


These scenarios demand high scale, to help make sure Bookings works well for you and scale to your needs, we have prepared these best practices.


1. Planning for scale

Each Bookings calendar is currently designed to handle a maximum of 2,500 bookings across all services in that calendar per day, along with a creation limit of 10 booking requests per second, this will work for common scenarios.

If your requirements exceed this, you should plan to distribute the load using the steps below.

  • Create a Bookings calendar with just one service.
  • Clone this calendar to multiple calendars.
  • You can opt-in to the Bookings preview to use a clone option and optout of the preview anytime you want to.
  • Limit each calendar for specific audiences, like:
        By buildings or operating group
        By booking period (mornings only vs afternoons)
  • Dividing the load across different Bookings calendars will help ensure none of them will reach the 2,500 limit.


2. Set how far in advance your customers can book an appointment

Finding the optimal value for the maximum advance appointment time your customers can book can help prioritize the daily limits for appointments that are closer to “today”. We have attached a simple Excel spreadsheet where you can enter the values to help you estimate the number of appointments and forward-looking time you can have in your Bookings calendar.

Follow the instructions below to use the attached spreadsheet.


  • Calculating the maximum advance appointment time in which those 2,500 appointments could be achieved.
  • Open the booking availability timeframe only for that period of time.
  • Keep updating the timeframe once the slots are full or a day has passed, so people will always have the option to book up to the same timeframe in advance.

If you got confused (don’t worry, we did too), below is an example. This example is calculated at the calendar level, not at the service level. 

  • If the appointment duration is 10 minutes, and the maximum number of working hours are 8, then the possible number of appointments/day will be 8*60/10. This means up to 48 appointments per staff member, assuming you don’t need buffer time between appointments.
  • If we consider 5 staff members per booking calendar, the max number of appointments you can have in a workday will be 240.
  • Considering that opening more than 2,500 slots will throttle the system, then the ability to book a service shouldn’t be opened for more than 2500/240 = ~10.5 days
  • Assuming a 5-day week, do not let your customers book appointments 2 weeks before the current date (I.e. today). This will ensure that your customers can always book an appointment
  • You can choose to move the booking timeframe every day to always have a 2 week pre-booking time or do it when your bookings are filling up.

We are actively working to increase the scaling limits as you read this and we will post a new communication as soon as our systems are updated.


Thank you!

Gabriel on behalf of the Bookings team

Version history
Last update:
‎Feb 03 2022 11:08 AM
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