55 Questions

Design a URL Shortening service like TinyURLEasy

Design PastebinEasy

Design InstagramEasy

Design Dropbox or Google DriveMedium

Design Facebook Messenger or WhatsAppMedium

Design Twitter for millions of usersEasy

Design Youtube or NetflixMedium

Design Typeahead Suggestion/AutocompleteHard

Design an API Rate LimiterHard

Design a Distributed Metrics Logging and Aggregation SystemVery Hard

Design a Distributed Stream Processing System like KafkaVery Hard

Design a Key-Value StoreMedium

Identify the K Most Shared Articles in Various Time Windows (24 hours, 1 hour, 5 minutes)Hard

Design Web CrawlerMedium

Design Facebook's News FeedMedium

Design Yelp or Nearby FriendsVery Hard

System to Collect Performance Metrics from Thousands of ServersHard

Design Google CalendarMedium

Design a Distributed Queue like RabbitMQHard

Design Google Analytics - User Analytics Dashboard and PipelineHard

Design a System for Sorting Large Data SetsEasy

Top K Elements: App Store Rankings, Amazon Bestsellers, etc.Easy

Design a Job SchedulerEasy

Design a Notification Service at ScaleHard

Surge Pricing System: Uber - Stream Processing, etc.Very Hard

Netflix: Limit the Number of Screens Each User Can WatchHard

Design an ETA Service and Location Sharing Between Driver and RiderVery Hard

Design a Hotel Booking System: Room Availability, Reservation, BookingMedium

Design an A/B Testing System (like Optimizely)Hard

Design a Price Alert System for Amazon (or for Stock prices)Easy

Design an IoC/Dependency Injection FrameworkVery Hard

Design a Credit Card Processing SystemVery Hard

Count Facebook Likes, Especially for High-Profile UsersMedium

Design a Control Plane for a Distributed DatabaseVery Hard

Design a User Login and Authentication System for a WebsiteMedium

Develop a Weather ApplicationEasy

Create a Document Management System like Wikipedia, Notion or Google DocsEasy

Build a Marketplace Feature for FacebookEasy

Design a System to Monitor the Health of a ClusterMedium

Find a Rider for Uber or Uber EatsHard

Design a Distributed Tracing SystemVery Hard

Design Backend for an App to Distribute 6 Million Free Burgers in One HourMedium

Design a File Downloader Library from Frontend to BackendHard

Design a System to View Latest Stock Prices WorldwideEasy

Develop a Photo Sharing Platform like Flickr or Google PhotosMedium

Design an On-Call Escalation SystemMedium

Design and Implement a Wire Transfer APIHard

Design a Live Comments Feature for FacebookHard

Design a Feature to Show the Number of Users Viewing a PageEasy

Design Facebook Likes Feature with Live UpdatesEasy

Create a System to Migrate Large Data to Google CloudVery Hard

Design a Distributed BotnetHard

Create a Distributed File Transfer System like BittorrentHard

Design a Parts Compatibility Feature for an eCommerce SiteEasy

Develop an Ads Management and Display System for a Social FeedVery Hard

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➡️

Count Facebook Likes, Especially for High-Profile Users

👷‍♂️ In progress: We are writing our own solutions

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📕 Here are some good solutions we found for this question:

Discussion on Blind: https://www.teamblind.com/post/System-Design-Question-How-does-FBInsta-storeretrieve-likes-NZEcwqVp

Detailed Solution: https://systemdesign.one/distributed-counter-system-design/

Video Solution: https://blog.interviewcamp.io/live-design-facebook-likes-distributed-counter

🙋

🙋 Here are some details you should know about this question:

To clarify: what scale are we looking at - what can the peak traffic be?

This is a distributed counters problem - how will you scale it as the likes grow?

How will you handle celebrity users, who get a huge number of counts really fast?

How do you deal with system failures? You will need some replication.

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