Design a doctor appointment booking system
PremiumMachine codingEasy
- Time slots
- Double booking
- Strategy pattern
Quick answer
This machine coding interview question asks you to design a doctor appointment booking system. Aim for a design that meets its requirements at the stated scale, then explain its main components, data flow and trade-offs. Interviewers want to see how you scope the problem, size it and defend each choice.
The problem
Build a doctor appointment booking system in memory, like the booking screen of a clinic app. Doctors publish 30-minute time slots, patients find doctors by specialisation and book a free slot. The hard part is small but real: no slot is ever booked twice and no patient is in two places at once.
The calendar covers one day. The system is a library with a small driver that runs the sample session below.
What must a doctor appointment booking system do?
- Add a doctor: addDoctor(name, specialisation, slots) returns a doctor id; slots are start times like 09:30, each 30 minutes long.
- Book: bookAppointment(patientId, doctorId, slotStart) books a free slot or fails with SLOT_NOT_OFFERED, SLOT_TAKEN or PATIENT_BUSY.
How well must it do it?
- No double booking: A slot holds at most one appointment, and a patient holds at most one appointment per start time.
- Easy to extend: The order of doctors in search can change without editing the booking code.
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- Time slots
- Double booking
- Strategy pattern
- Slot validation
- Enum modelling
- Unit testing
How you’ll practise
- Requirements
- Entities and interfaces
- Core implementation
- Edge cases and tests
- Extensions
- Wrap-up
Lala, personalized to you, gives a hint when you ask and reviews your design when you are ready.
What do interviewers look for?
In any machine coding design round.
- Clarifies the requirements before drawing anything
- Uses a few numbers that actually change the design
- Draws a clear path from the client to storage
- Picks storage and caching with reasons, not by habit
- Explains what breaks first under load and how to fix it
- States trade-offs openly instead of claiming a perfect design
Questions people ask about this interview question
- Which design type is this question?
- It is a machine coding question. You design a doctor appointment booking system and explain your choices the way you would in an interview.
- Is this question asked at entry level?
- It is marked Easy, so it suits engineers who are new to machine coding interviews. It is also a good warm-up before harder questions.
- What should I cover first?
- Start with the requirements: what the system must do, how well it must do it and which numbers change the design. Agree on scope with the interviewer before you design anything.
- Can I practise it for free?
- It is a premium question. Sign up and unlock it once for 10 credits; it then stays unlocked. When you finish, Lala, your personalized AI mentor, can review your design for 30 credits.
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Updated · Written by the SevyDevy team