Design
Contact Management System (Address Book)
Design an address book application that stores contacts, supports search, and groups contacts into categories.
01 - Why interviewers ask this
It looks simple but rewards candidates who think about real-world messiness — duplicate detection, fast partial search — instead of treating it as a plain CRUD list.
02 - Where this system exists in the real world
You interact with this design every day.
Phone/email address book apps
CRM contact databases
Corporate directory and org-chart tools
03 - What you'll master
Solve this once. Know it forever.
Design fast partial-match search (trie/index)
Implement duplicate detection and merging
Model many-to-many contact-to-group relationships
04 - What you'll design
6 functional · 2 non-functional requirements.
Add, edit, and delete a contact (name, phone, email, address)
5 more requirements inside
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05 - Companies that ask this
You may face this exact question in your next interview.
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