Design a Calendar Application (Meeting Scheduler)
Last Updated: July 16, 2025
Design a Calendar Application that allows users to create, update, delete, and view events with support for reminders, recurring events, and conflict detection.
A Calendar Application is a digital scheduling tool that helps users organize their time, manage events, and stay on top of personal or professional commitments.
It provides an interface to view daily, weekly, or monthly schedules and includes features like:
- Event creation with custom titles, times, and descriptions
- Support for single or recurring events (e.g., daily stand-ups, monthly meetings)
- Notifications or reminders before upcoming events
- Conflict detection to avoid overlapping bookings
In this chapter, we will explore the low-level design of a calendar application in detail.
Let's start by clarifying the requirements:
1. Clarifying Requirements
Before starting the design, it's important to ask thoughtful questions to uncover hidden assumptions and better define the scope of the system.
Here is an example of how a conversation between the candidate and the interviewer might unfold:
Candidate: Should the system support recurring meetings, or only one-time events?
Interviewer: Let’s keep it simple for now and only support one-time (non-recurring) meetings.
Candidate: Should users be able to set their availability and working hours, and should the system respect this when suggesting meeting slots?
Interviewer: Yes, users should be able to define their working hours and mark time slots as busy or available. Meetings should only be scheduled during available hours.
Candidate: Should users be able to reserve meeting rooms as part of scheduling a meeting?
Interviewer: Yes, meeting rooms are shared resources. They should be reservable during meeting creation, and a room must not be double-booked.
Candidate: Should the system send notifications when meetings are scheduled or updated?
Interviewer: Yes, all attendees should receive notifications when a meeting is scheduled, or canceled.
Candidate: Should the system detect and prevent scheduling conflicts, such as overlapping meetings or double bookings?
Interviewer: Yes, the system should prevent overlapping meetings for users and meeting rooms.
After gathering the details, we can summarize the key system requirements.
1.1 Functional Requirements
- Allow users to create, cancel, and view meetings
- Support scheduling meeting between multiple users while respecting each user's availability hours.
- Allow booking of meeting rooms and ensure no room is double-booked.
- Notify users when meetings are created, or canceled
- Display user calendars showing busy and available time slots
- Support time-based filtering (e.g., view today’s schedule, this week, etc.)
1.2 Non-Functional Requirements
- Modularity: The system should follow object-oriented design principles with clear separation of components.
- Consistency: All calendar updates must be atomic and prevent conflicts (e.g., no two meetings at the same time for the same user).
- Scalability: The system should efficiently handle thousands of users, meetings, and room bookings.
- Extensibility: The design should be easy to extend to support future features such as recurring meetings, and attendee responses (accept/decline)
- Usability: The system should provide a clean interface for scheduling and browsing meetings, with clear feedback on success or failure