Top 40+ Grokking the System Design Interview Questions and Answers

Are you preparing for grokking the system design interviews? To help you out, we’ve compiled over 40 common system design interview questions with detailed answers. This comprehensive guide helps you understand the key considerations and approaches for designing scalable and efficient systems.

Top 40+ Grokking the System Design Interview Questions and Answers

1. Design a URL Shortening Service (e.g., TinyURL)
2. Design a Pastebin Service.
3. Design a File Storage Service (e.g., Dropbox)
4. Design a Messaging Service (e.g., WhatsApp)
5. Design a Social Media Feed (e.g., Facebook Newsfeed)
6. Design a Ride-Sharing Service (e.g., Uber)
7. Design a Video Streaming Service (e.g., YouTube)
8. Design a Search Engine
9. Design a Content Delivery Network (CDN)
10. Design a Notification System
11. Design a Rate Limiter
12. Design a Web Crawler
13. Design a Recommendation System
14. Design a Distributed Cache
15. Design a Ticket Booking System
16. Design a Logging and Monitoring System
17. Design a Metrics Collection and Reporting System
18. Design a Chat Application
19. Design a Payment Processing System
20. Design a Document Collaboration System (e.g., Google Docs)
21. Design a Real-Time Collaborative Whiteboard
22. Design a URL Shortening Service (e.g., Bitly)
23. Design a Video Streaming Platform (e.g., Netflix)
24. Design a Distributed Task Scheduler
25. Design a Geolocation-Based Service (e.g., Find My Friends)
26. Design a Real-Time Analytics Dashboard
27. Design a Multi-Tenant SaaS Application
28. Design a Real-Time Multiplayer Game Backend
29. Design a Feature Flag Management System
30. Design a Document Version Control System
31. Design a Real-Time Stock Trading Platform
32. Design a Content Moderation System
33. Design a Real-Time Bidding System for Online Advertising
34. Design a Social Media Feed
35. Design a Ride-Sharing Service (e.g., Uber)
36. Design a Video Conferencing System (e.g., Zoom)
37. Design a Cloud Storage Service (e.g., Dropbox)
38. Design a News Aggregator
39. Design a Real-Time Chat Application
40. Design a URL Shortening Service
41. Design a Video Streaming Platform
42. Design a Distributed Task Scheduler
43. Design a Geolocation-Based Service

1. Design a URL Shortening Service (e.g., TinyURL)

Requirements:

• Generate a unique short URL for a given long URL.
• Redirect short URLs to the original long URLs.
• Handle high read and write traffic efficiently.
• Ensure the system is highly available and scalable.

Design Considerations:

• API Endpoints: Define APIs for creating and retrieving URLs.
• Database Schema: Use a key-value store where the key is the short URL and the value is the long URL.
• Unique ID Generation: Implement a base62 encoding of auto-incrementing IDs or use hash functions to generate unique short URLs.
• Redirection Mechanism: Use HTTP 302 status codes for redirection.
• Scalability: Employ load balancers and database sharding to handle high traffic.
• Caching: Utilize caching mechanisms to store frequently accessed URLs and reduce database load.

2. Design a Pastebin Service

Requirements:

• Allow users to paste text or code snippets.
• Generate a unique URL for each paste.
• Support public and private pastes.
• Implement expiration times for pastes.

Design Considerations:

• API Endpoints: Create APIs for creating, retrieving, and deleting pastes.
• Database Schema: Store pastes with fields for content, unique URL, privacy settings, expiration time, and metadata.
• Unique URL Generation: Similar to URL shortening, use base62 encoding or hash functions.
• Expiration Handling: Implement background jobs to delete expired pastes.
• Scalability: Use load balancers and partition the database to manage high traffic.
• Security: Ensure proper authentication and authorization for private pastes.

3.Design a File Storage Service (e.g., Dropbox)

Requirements:

• Allow users to upload, download, and delete files.
• Support file synchronization across devices.
• Handle large file sizes and concurrent uploads/downloads.
• Ensure data consistency and integrity.

Design Considerations:

• API Endpoints: Develop APIs for file operations and synchronization.
• Storage System: Use distributed file storage systems like HDFS or cloud storage solutions.
• Metadata Management: Maintain metadata for files, including versioning, permissions, and synchronization status.
• Data Consistency: Implement mechanisms like conflict resolution and eventual consistency models.
• Scalability: Use content delivery networks (CDNs) and load balancers to handle large-scale data transfer.
• Security: Encrypt data at rest and in transit, and implement robust authentication mechanisms.

4. Design a Messaging Service (e.g., WhatsApp)

Requirements:

• Support real-time messaging between users.
• Handle group chats and multimedia messages.
• Ensure message delivery guarantees (e.g., at least once delivery).
• Provide end-to-end encryption.

Design Considerations:

• API Endpoints: Create APIs for sending, receiving, and managing messages.
• Message Queues: Use message brokers like Kafka or RabbitMQ to handle message delivery.
• Storage: Store messages in databases with appropriate indexing for quick retrieval.
• Real-time Communication: Implement WebSocket connections for real-time message delivery.
• Scalability: Use load balancers and partitioning to manage high user traffic.
• Security: Implement end-to-end encryption and secure authentication mechanisms.

5. Design a Social Media Feed (e.g., Facebook Newsfeed)

Requirements:

• Display a personalized feed of posts for each user.
• Support various content types (text, images, videos).
• Handle high read and write operations.
• Ensure low latency and high availability.

Design Considerations:

• Feed Generation: Use pull, push, or hybrid models to generate user feeds.
• Storage: Store posts and user interactions in databases optimized for read-heavy operations.
• Caching: Implement caching strategies to reduce database load and improve response times.
• Scalability: Use load balancers, database sharding, and CDNs to handle large-scale data.
• Personalization: Implement algorithms to rank and personalize feed content based on user preferences and interactions.

6. Design a Ride-Sharing Service (e.g., Uber)

Requirements:

• Match riders with nearby drivers in real-time.
• Provide accurate and efficient route planning.
• Handle surge pricing and demand prediction.
• Ensure system reliability and scalability.

Design Considerations:

• Real-time Matching: Use location-based services and geospatial indexing to match riders with drivers.
• Routing: Integrate with mapping services for route optimization and ETA calculations.
• Scalability: Implement microservices architecture to handle different functionalities independently.
• Data Storage: Use databases optimized for geospatial queries and real-time data.
• Load Balancing: Distribute incoming requests across multiple servers to ensure high availability.
• Analytics: Implement data analytics for demand prediction and surge pricing algorithms.

7. Design a Video Streaming Service (e.g., YouTube)

Requirements:

• Allow users to upload, stream, and share videos.
• Support various video formats and resolutions.
• Handle high concurrent streaming sessions.
• Provide recommendations and search functionality.

Design Considerations:

• Storage: Use distributed storage systems to store video files.
• Transcoding: Implement video transcoding to support multiple formats and resolutions.
• Content Delivery: Use CDNs to deliver video content efficiently to users worldwide.
• Metadata Management: Store metadata for videos, including titles, descriptions, tags, and user interactions.
• Scalability: Use load balancers and microservices to handle different functionalities.
• Recommendations: Implement algorithms to provide personalized video recommendations.

8. Design a Search Engine

Requirements:

• Crawl and index web pages efficiently.
• Provide relevant search results with low latency.
• Handle a large volume of search queries.
• Support ranking algorithms and personalization.

Design Considerations:

• Web Crawling: Implement distributed web crawlers to gather data from the internet.
• Indexing: Use inverted indexes to store and retrieve search data efficiently.
• Ranking: Develop ranking algorithms to order search results based on relevance.
• Scalability: Use distributed systems and load balancers to handle high query volumes.
• Caching: Implement caching strategies to reduce latency for frequent queries.
• Personalization: Use user data to provide personalized search results.

9. Design a Content Delivery Network (CDN)

Requirements:

• Distribute content to users with low latency.
• Handle high traffic and provide high availability.
• Support various content types (e.g., images, videos, documents).
• Ensure data consistency and integrity.

Design Considerations:

• Edge Servers: Deploy servers in multiple geographic locations to cache content closer to users, reducing latency.
• Load Balancing: Distribute incoming requests across edge servers to prevent overloading and ensure high availability.
• Caching Strategies: Implement caching mechanisms with appropriate expiration policies to serve content efficiently.
• Content Invalidation: Develop mechanisms to update or invalidate cached content when the origin content changes.
• Security: Ensure secure data transmission using protocols like HTTPS and implement DDoS protection measures.
• Monitoring: Continuously monitor server performance and user access patterns to optimize content delivery.

10. Design a Notification System

Requirements:

• Send notifications to users via multiple channels (e.g., email, SMS, push notifications).
• Ensure timely and reliable delivery of notifications.
• Handle high volumes of notifications.
• Support user preferences and opt-in/opt-out mechanisms.

Design Considerations:

• Message Queue: Use message queuing systems to handle and prioritize notification delivery.
• Worker Services: Implement worker services to process messages from the queue and send notifications through appropriate channels.
• User Preferences: Maintain user preferences regarding notification channels and frequency.
• Retry Mechanism: Implement retry logic for failed notification deliveries.
• Scalability: Design the system to scale horizontally to handle increasing notification volumes.
• Logging and Monitoring: Log notification events and monitor system performance to ensure reliability.

11. Design a Rate Limiter

Requirements:

• Limit the number of requests a user or service can make to an API within a specified time frame.
• Prevent abuse and ensure fair usage of resources.
• Provide flexibility to define different rate limits for different users or services.

Design Considerations:

• Token Bucket Algorithm: Implement the token bucket algorithm to control the rate of requests.
• Distributed Environment: Ensure the rate limiter works effectively in a distributed system by using centralized data stores or distributed caches.
• User Identification: Identify users or services using API keys or authentication tokens.
• Flexibility: Allow configuration of different rate limits based on user roles or subscription plans.
• Logging and Monitoring: Log rate-limiting events and monitor the system to detect and respond to abuse patterns.

12. Design a Web Crawler

Requirements:

• Efficiently crawl and index web pages from the internet.
• Respect the robots.txt directives of websites.
• Handle large-scale data and ensure freshness of the indexed content.

Design Considerations:

• URL Frontier: Maintain a queue of URLs to be crawled, prioritizing based on factors like page rank and update frequency.
• Politeness Policy: Implement delays between requests to the same server to avoid overloading websites.
• Distributed Crawling: Use multiple crawling agents distributed across different servers to increase efficiency.
• Content Storage: Store crawled data in a scalable storage system, indexing content for efficient retrieval.
• Duplicate Detection: Implement mechanisms to detect and handle duplicate content.
• Scalability: Design the system to scale horizontally to handle the vast amount of web data.

13. Design a Recommendation System

Requirements:

• Provide personalized recommendations to users based on their behavior and preferences.
• Handle large datasets and provide real-time recommendations.
• Ensure scalability and adaptability to changing user behaviors.

Design Considerations:

• Collaborative Filtering: Use user-item interaction data to recommend items that similar users have liked.
• Content-Based Filtering: Recommend items similar to those a user has liked, based on item attributes.
• Hybrid Approach: Combine collaborative and content-based filtering to improve recommendation accuracy.
• Real-Time Processing: Implement real-time data processing pipelines to update recommendations promptly.
• Scalability: Use distributed computing frameworks to handle large-scale data processing.
• Evaluation Metrics: Regularly evaluate the recommendation system using metrics like precision, recall, and user satisfaction.

14. Design a Distributed Cache

Requirements:

• Provide a caching layer to store frequently accessed data.
• Ensure high availability and fault tolerance.
• Support scalability to handle increasing data loads.

Design Considerations:

• Data Partitioning: Use consistent hashing to distribute data across multiple cache nodes.
• Replication: Replicate data across nodes to ensure fault tolerance.
• Eviction Policies: Implement eviction policies like Least Recently Used (LRU) to manage cache size.
• Consistency: Choose between strong and eventual consistency models based on application requirements.
• Scalability: Design the system to add or remove cache nodes without significant downtime.
• Monitoring: Implement monitoring tools to track cache performance and hit/miss ratios.

15. Design a Ticket Booking System

Requirements:

• Allow users to search for and book tickets (e.g., movies, flights).
• Handle concurrent bookings and prevent overbooking.
• Provide real-time availability updates.

Design Considerations:

• Inventory Management: Maintain an accurate count of available tickets and update in real-time.
• Concurrency Control: Implement locking mechanisms or optimistic concurrency control to handle simultaneous booking attempts.
• Reservation System: Introduce a temporary reservation period during which the user must complete the booking; otherwise, the tickets are released back to the pool.
• Scalability: Design the system to handle high traffic during peak booking times.
• Payment Processing: Integrate with reliable payment gateways and ensure secure transactions.
• Notification Service: Send confirmations and reminders to users via email or SMS.

16. Design a Logging and Monitoring System

Requirements:

• Collect and store logs from various services and applications.
• Provide real-time monitoring and alerting.
• Support querying and analysis of log data.

Design Considerations:

• Log Collection: Use agents or daemons to collect logs from different sources and forward them to a central system.
• Storage: Store logs in a scalable and searchable database, such as Elasticsearch.
• Real-time Processing: Implement stream processing to analyze logs in real-time and trigger alerts.
• Visualization: Use dashboards to visualize metrics and trends.
• Alerting: Set up thresholds and rules to send alerts via email, SMS, or other channels when anomalies are detected.
• Retention Policies: Define how long logs are stored and implement mechanisms to archive or delete old logs.

17. Design a Metrics Collection and Reporting System

Requirements:

• Collect metrics from various services and applications.
• Provide dashboards and reports for analysis.
• Support real-time and historical data analysis.

Design Considerations:

• Data Collection: Use agents to collect metrics and send them to a central system.
• Storage: Store metrics in time-series databases optimized for this type of data.
• Visualization: Provide dashboards with customizable views for different metrics.
• Alerting: Set up alerts for specific metric thresholds or anomalies.
• Scalability: Ensure the system can handle a high volume of metrics from numerous sources.
• Data Retention: Implement policies for data retention and aggregation to manage storage costs.

18. Design a Chat Application

Requirements:

• Support one-on-one and group chats.
• Provide real-time message delivery.
• Support multimedia messages (e.g., images, videos).
• Ensure message history is stored and retrievable.

Design Considerations:

• Real-time Communication: Use WebSockets or similar technologies for instant message delivery.
• Message Storage: Store messages in databases with appropriate indexing for quick retrieval.
• Scalability: Design the system to handle a large number of concurrent users and messages.
• Multimedia Support: Implement storage and retrieval mechanisms for multimedia content.
• Security: Ensure end-to-end encryption and secure authentication mechanisms.
• Offline Support: Allow users to receive messages sent while they were offline once they reconnect.

19. Design a Payment Processing System

Requirements:

• Process payments securely and efficiently.
• Support multiple payment methods (e.g., credit cards, digital wallets).
• Handle refunds and chargebacks.
• Ensure compliance with financial regulations.

Design Considerations:

• Payment Gateway Integration: Integrate with reliable payment gateways to process transactions.
• Security: Implement encryption, tokenization, and comply with standards like PCI DSS.
• Transaction Management: Maintain records of all transactions and their statuses.
• Scalability: Design the system to handle high transaction volumes, especially during peak times.
• Fraud Detection: Implement mechanisms to detect and prevent fraudulent activities.
• Compliance: Ensure the system adheres to relevant financial regulations and standards.

20. Design a Document Collaboration System (e.g., Google Docs)

Requirements:

• Allow multiple users to edit documents simultaneously.
• Provide real-time updates to all collaborators.
• Maintain version history and support undo/redo operations.
• Ensure data consistency and conflict resolution.

Design Considerations:

• Real-time Collaboration: Use Operational Transformation (OT) or Conflict-free Replicated Data Types (CRDTs) to handle concurrent edits.
• Data Storage: Store documents in databases optimized for real-time updates and retrieval.
• Version Control: Maintain a history of changes to support versioning and rollback.
• Scalability: Ensure the system can handle a large number of concurrent users and documents.
• Security: Implement access controls, encryption, and secure authentication mechanisms.
• Offline Support: Allow users to edit documents offline and synchronize changes once they reconnect.

21. Design a Real-Time Collaborative Whiteboard

Requirements:

• Enable multiple users to draw and edit simultaneously.
• Provide real-time updates to all participants.
• Support various drawing tools and shapes.
• Maintain a history of changes for undo/redo functionality.

Design Considerations:

• Real-Time Communication: Utilize WebSockets or similar protocols to facilitate instant updates among users.
• Data Synchronization: Implement Operational Transformation (OT) or Conflict-free Replicated Data Types (CRDTs) to manage concurrent edits and ensure consistency.
• State Management: Maintain the current state of the whiteboard on the server, allowing new participants to synchronize upon joining.
• Scalability: Design the system to handle numerous concurrent sessions and users, possibly by partitioning sessions across multiple servers.
• Persistence: Store session data to allow users to save and revisit their whiteboards.
• Security: Implement authentication and authorization to control access to sessions.

22. Design a URL Shortening Service (e.g., Bitly)

Requirements:

• Generate a unique short URL for a given long URL.
• Redirect short URLs to the original long URLs.
• Track analytics such as click counts.
• Handle high read and write traffic efficiently.

Design Considerations:

• Unique ID Generation: Use base62 encoding of auto-incrementing IDs or hash functions to generate unique short URLs.
• Database Schema: Employ a key-value store where the key is the short URL and the value is the long URL.
• Redirection Mechanism: Implement HTTP 302 status codes for redirection.
• Analytics Tracking: Store metadata such as click counts, timestamps, and referrer information.
• Scalability: Utilize load balancers and database sharding to manage high traffic.
• Caching: Implement caching strategies to store frequently accessed URLs and reduce database load.

23. Design a Video Streaming Platform (e.g., Netflix)

Requirements:

• Allow users to stream videos on demand.
• Support various devices and network conditions.
• Provide personalized content recommendations.
• Ensure minimal buffering and high-quality playback.

Design Considerations:

• Content Delivery: Use Content Delivery Networks (CDNs) to distribute video content closer to users, reducing latency.
• Adaptive Streaming: Implement protocols like HTTP Live Streaming (HLS) to adjust video quality based on network conditions.
• Transcoding: Convert videos into multiple formats and resolutions to support various devices.
• Recommendation System: Utilize collaborative filtering and content-based filtering to provide personalized recommendations.
• Scalability: Design the system to handle a large number of concurrent streams, employing microservices architecture and load balancing.
• Data Analytics: Collect and analyze user engagement metrics to optimize content delivery and recommendations.

24. Design a Distributed Task Scheduler

Requirements:

• Schedule and execute tasks across multiple servers.
• Ensure fault tolerance and high availability.
• Support task dependencies and priorities.
• Provide monitoring and logging of task execution.

Design Considerations:

• Task Queue: Use distributed message queues to manage task distribution among workers.
• Worker Nodes: Deploy worker nodes that poll the queue, execute tasks, and report results.
• Fault Tolerance: Implement retry mechanisms and task acknowledgment to handle failures.
• Scheduling Logic: Allow for cron-like scheduling, one-time tasks, and support for task dependencies.
• Scalability: Enable dynamic scaling of worker nodes based on the task load.
• Monitoring: Provide dashboards and alerts for task statuses, failures, and performance metrics.

25. Design a Geolocation-Based Service (e.g., Find My Friends)

Requirements:

• Allow users to share their real-time location with friends.
• Provide notifications when friends are nearby.
• Ensure user privacy and data security.
• Handle a large number of concurrent users.

Design Considerations:

• Location Updates: Implement efficient mechanisms for users to share and update their location periodically.
• Proximity Detection: Use geospatial indexing to detect when users are within a certain distance of each other.
• Privacy Controls: Allow users to control who can see their location and provide options to hide or share selectively.
• Scalability: Design the system to handle real-time location updates from millions of users, possibly using partitioning and load balancing.
• Data Storage: Store location history securely and ensure compliance with data protection regulations.
• Notifications: Implement push notifications to alert users when friends are nearby, ensuring minimal latency.

26. Design a Real-Time Analytics Dashboard

Requirements:

• Display real-time metrics and KPIs.
• Support customizable widgets and views.
• Handle high-frequency data updates.
• Ensure data accuracy and consistency.

Design Considerations:

• Data Ingestion: Use stream processing frameworks to handle incoming data in real-time.
• Storage: Employ time-series databases optimized for high-write and read operations.
• Data Aggregation: Implement aggregation logic to compute metrics over various time windows.
• WebSocket Communication: Use WebSockets to push real-time updates to the dashboard frontend.
• Scalability: Design the system to scale horizontally to accommodate increasing data volumes and user traffic.
• User Customization: Allow users to create and customize widgets, saving their preferences securely.

27. Design a Multi-Tenant SaaS Application

Requirements:

• Support multiple tenants (organizations) with data isolation.
• Allow tenant-specific customizations.
• Ensure scalability and high availability.
• Implement robust security measures.

Design Considerations:

• Tenant Isolation: Decide between database-per-tenant, schema-per-tenant, or shared schema with tenant identifiers to isolate data.
• Customization: Allow tenants to customize features, UI, and workflows without affecting others.
• Scalability: Design the system to scale horizontally, adding resources as the number of tenants grows.
• Security: Implement strong authentication, authorization, and encryption mechanisms to protect tenant data.
• Resource Allocation: Monitor and allocate resources to ensure fair usage among tenants.
• Maintenance: Plan for seamless updates and maintenance without disrupting tenant operations.

28. Design a Real-Time Multiplayer Game Backend

Requirements:

• Support real-time interactions between players.
• Ensure low latency and synchronization.
• Handle matchmaking and game state management.
• Provide scalability to accommodate a large number of concurrent players.

Design Considerations:

• Real-Time Communication: Use UDP or WebSockets for low-latency communication between clients and servers.
• Game State Management: Maintain authoritative game state on the server to prevent cheating and ensure consistency.
• Matchmaking: Implement algorithms to pair players based on skill level, location, or other criteria.
• Scalability: Use a microservices architecture to handle different game components and scale them independently.
• Load Balancing: Distribute players across multiple servers to balance the load and prevent bottlenecks.
• Security: Implement measures to detect and prevent cheating, such as server-side validation and anomaly detection.

29. Design a Feature Flag Management System

Requirements:

• Enable or disable features dynamically without deploying new code.
• Support targeting specific user segments.
• Provide a dashboard for managing feature flags.
• Ensure minimal performance overhead.

Design Considerations:

• Configuration Storage: Store feature flag configurations in a centralized, scalable database.
• SDKs: Provide client libraries for different platforms to evaluate feature flags locally.
• Targeting Rules: Allow defining rules to enable or disable features for specific user segments based on attributes.
• Real-Time Updates: Implement mechanisms to propagate configuration changes to clients in real-time.
• Performance: Optimize the system to minimize latency and overhead during feature flag evaluation.
• Audit Logging: Maintain logs of changes to feature flags for auditing and troubleshooting purposes.

30. Design a Document Version Control System

Requirements:

• Track changes to documents over time.
• Support branching and merging of document versions.
• Allow collaborative editing with conflict resolution.
• Provide a history of changes with the ability to revert to previous versions.

Design Considerations:

• Data Storage: Use a storage system that supports efficient diffing and storage of document versions.
• Branching and Merging: Implement mechanisms to create branches for parallel edits and merge changes with conflict resolution strategies.
• Collaboration: Provide real-time collaboration features with locking mechanisms to prevent conflicts.
• Version History: Maintain a comprehensive history of changes with metadata such as author, timestamp, and commit messages.
• Access Control: Implement permissions to control who can view or edit specific versions or branches.
• Scalability: Design the system to handle a large number of documents and concurrent users.

31. Design a Real-Time Stock Trading Platform

Requirements:

• Allow users to buy and sell stocks in real-time.
• Provide real-time market data and updates.
• Ensure high availability and low latency.
• Implement robust security and compliance measures.

Design Considerations:

• Order Matching Engine: Develop a high-performance engine to match buy and sell orders efficiently.
• Market Data Feed: Integrate with stock exchanges to receive real-time market data and disseminate it to users.
• Scalability: Design the system to handle high volumes of transactions and user activity, especially during market peaks.
• Latency: Optimize network and processing paths to minimize latency in order execution and data delivery.
• Security: Implement strong authentication, encryption, and fraud detection mechanisms to protect user data and transactions.
• Compliance: Ensure the platform adheres to financial regulations and maintains audit trails for all transactions.

32. Design a Content Moderation System

Requirements:

• Automatically detect and flag inappropriate content.
• Support multiple content types, including text, images, and videos.
• Allow human moderators to review flagged content.
• Provide tools for users to report content.

Design Considerations:

• Automated Detection: Use machine learning models to detect spam, hate speech, nudity, and other inappropriate content.
• Human Review: Implement workflows for human moderators to review and take action on flagged content.
• User Reporting: Provide interfaces for users to report content, which feeds into the moderation workflow.
• Scalability: Design the system to handle large volumes of content and scale with user growth.
• Audit Logging: Maintain logs of moderation actions for accountability and compliance purposes.
• Feedback Loop: Use outcomes from human reviews to retrain and improve automated detection models.

33. Design a Real-Time Bidding System for Online Advertising

Requirements:

• Enable advertisers to bid for ad impressions in real-time.
• Ensure low-latency processing to handle high-frequency auctions.
• Support multiple ad formats and targeting criteria.
• Provide analytics and reporting for advertisers and publishers.

Design Considerations:

• Ad Exchange: Serve as a central platform connecting advertisers and publishers, facilitating real-time auctions for ad impressions.
• Demand-Side Platform (DSP): Allow advertisers to set bidding strategies, budgets, and targeting parameters.
• Supply-Side Platform (SSP): Enable publishers to offer their ad inventory and set floor prices.
• Bid Request and Response: Implement a protocol for sending bid requests to multiple DSPs and receiving bids within milliseconds.
• Auction Mechanism: Conduct auctions (e.g., second-price auctions) to determine the winning bid for each impression.
• Latency Optimization: Optimize network and processing paths to ensure auctions complete within strict time constraints.
• Scalability: Design the system to handle billions of ad impressions daily, scaling horizontally as needed.
• Data Analytics: Provide real-time dashboards and reports for performance monitoring and decision-making.
• Security and Fraud Detection: Implement measures to detect and prevent fraudulent activities, ensuring the integrity of the bidding process.

34. Design a Social Media Feed

Requirements:

• Display a personalized feed of posts from friends and followed entities.
• Support various content types, including text, images, and videos.
• Ensure real-time updates as new content is posted.
• Handle high read and write traffic efficiently.

Design Considerations:

• Feed Generation: Use a combination of pull and push models to generate and update user feeds.
• Content Ranking: Implement algorithms to rank content based on relevance, recency, and user engagement.
• Caching: Cache frequently accessed feeds to reduce database load and improve response times.
• Scalability: Partition data and use load balancing to handle a large number of concurrent users.
• Real-Time Updates: Utilize WebSockets or long polling to push new content to users in real-time.
• Content Moderation: Implement mechanisms to detect and handle inappropriate content.

35. Design a Ride-Sharing Service (e.g., Uber)

Requirements:

• Connect riders with nearby drivers.
• Provide real-time tracking of vehicles.
• Calculate fares based on distance and time.
• Handle surge pricing during high-demand periods.

Design Considerations:

• Matching Algorithm: Develop algorithms to match riders with the most suitable drivers based on proximity and other factors.
• Real-Time Tracking: Use GPS data to provide real-time tracking of vehicles for riders and drivers.
• Pricing Engine: Calculate fares dynamically, incorporating factors like distance, time, and demand.
• Scalability: Design the system to handle high volumes of requests, especially during peak times.
• Reliability: Ensure high availability and fault tolerance to provide a seamless user experience.
• Payment Processing: Integrate secure payment gateways to handle transactions.

36. Design a Video Conferencing System (e.g., Zoom)

Requirements:

• Support real-time audio and video communication.
• Allow multiple participants in a single meeting.
• Provide screen sharing and recording features.
• Ensure low latency and high-quality streams.

Design Considerations:

• Media Servers: Use media servers to handle audio and video streams, including mixing and transcoding.
• Signaling: Implement signaling protocols to establish and manage connections between participants.
• Scalability: Design the system to support a large number of concurrent meetings and participants.
• Quality of Service (QoS): Implement mechanisms to adapt to varying network conditions, ensuring optimal audio and video quality.
• Security: Ensure end-to-end encryption and secure authentication mechanisms.
• Cross-Platform Support: Develop clients for various platforms, including web, mobile, and desktop.

37. Design a Cloud Storage Service (e.g., Dropbox)

Requirements:

• Allow users to store and sync files across devices.
• Provide sharing and collaboration features.
• Ensure data durability and availability.
• Support versioning and recovery of deleted files.

Design Considerations:

• Data Storage: Use distributed storage systems to store user files, ensuring redundancy and durability.
• File Synchronization: Implement mechanisms to detect file changes and sync them across devices in real-time.
• Sharing and Permissions: Allow users to share files and folders with others, managing permissions appropriately.
• Scalability: Design the system to handle a large number of users and files, scaling horizontally as needed.
• Security: Implement encryption for data at rest and in transit, along with robust authentication mechanisms.
• Versioning: Maintain versions of files to allow users to revert to previous states or recover deleted files.

38. Design a News Aggregator

Requirements:

• Collect news articles from various sources.
• Categorize and rank articles based on relevance and user preferences.
• Provide personalized news feeds.
• Ensure timely updates as new articles are published.

Design Considerations:

• Content Crawling: Develop crawlers to fetch articles from various news websites and RSS feeds.
• Data Processing: Extract metadata, categorize articles, and remove duplicates.
• Personalization: Use machine learning algorithms to recommend articles based on user interests and reading history.
• Scalability: Design the system to handle a large number of sources and users, scaling horizontally as needed.
• Real-Time Updates: Implement mechanisms to detect and fetch new articles promptly.
• User Interface: Provide a clean and intuitive interface for users to read and interact with articles.

39. Design a Real-Time Chat Application

Requirements:

• Support one-on-one and group chats.
• Provide real-time message delivery.
• Ensure message history is stored and retrievable.
• Support multimedia messages (e.g., images, videos).

Design Considerations:

• Real-Time Communication: Use WebSockets or similar technologies for instant message delivery.
• Message Storage: Store messages in databases with appropriate indexing for quick retrieval.
• Scalability: Design the system to handle a large number of concurrent users and messages.
• Multimedia Support: Implement storage and retrieval mechanisms for multimedia content.
• Security: Ensure end-to-end encryption and secure authentication mechanisms.
• Offline Support: Allow users to receive messages sent while they were offline once they reconnect.

40. Design a URL Shortening Service

Requirements:

• Generate a unique short URL for a given long URL.
• Redirect short URLs to the original long URLs.
• Track analytics such as click counts.
• Handle high read and write traffic efficiently.

Design Considerations:

• Unique ID Generation: Use base62 encoding of auto-incrementing IDs or hash functions to generate unique short URLs.
• Database Schema: Employ a key-value store where the key is the short URL and the value is the long URL.
• Redirection Mechanism: Implement HTTP 302 status codes for redirection.
• Analytics Tracking: Store metadata such as click counts, timestamps, and referrer information.
• Scalability: Utilize load balancers and database sharding to manage high traffic.
• Caching: Implement caching strategies to store frequently accessed URLs and reduce database load.

41. Design a Video Streaming Platform

Requirements:

• Allow users to stream videos on demand.
• Support various devices and network conditions.
• Provide personalized content recommendations.
• Ensure minimal buffering and high-quality playback.

Design Considerations:

• Content Delivery: Use Content Delivery Networks (CDNs) to distribute video content closer to users, reducing latency.
• Adaptive Streaming: Implement protocols like HTTP Live Streaming (HLS) to adjust video quality based on network conditions.
• Transcoding: Convert videos into multiple formats and resolutions to support various devices.
• Recommendation System: Utilize collaborative filtering and content-based filtering to provide personalized recommendations.
• Scalability: Design the system to handle a large number of concurrent streams, employing microservices architecture and load balancing.
• Data Analytics: Collect and analyze user engagement metrics to optimize content delivery and recommendations.

42. Design a Distributed Task Scheduler

Requirements:

• Schedule and execute tasks across multiple servers.
• Ensure fault tolerance and high availability.
• Support task dependencies and priorities.
• Provide monitoring and logging of task execution.

Design Considerations:

• Task Queue: Use distributed message queues to manage task distribution among workers.
• Worker Nodes: Deploy worker nodes that poll the queue, execute tasks, and report results.
• Fault Tolerance: Implement retry mechanisms and task acknowledgment to handle failures.
• Scheduling Logic: Allow for cron-like scheduling, one-time tasks, and support for task dependencies.
• Scalability: Enable dynamic scaling of worker nodes based on the task load.
• Monitoring: Provide dashboards and alerts for task statuses, failures, and performance metrics.

43. Design a Geolocation-Based Service

Requirements:

• Allow users to share their real-time location with friends.
• Provide notifications when friends are nearby.
• Ensure user privacy and data security.
• Handle a large number of concurrent users.

Design Considerations:

• Notifications: Implement push notifications to alert users when friends are nearby, ensuring minimal latency.
• Location Updates: Implement efficient mechanisms for users to share and update their location periodically.
• Proximity Detection: Use geospatial indexing to detect when users are within a certain distance of each other.
• Privacy Controls: Allow users to control who can see their location and provide options to hide or share selectively.
• Scalability: Design the system to handle real-time location updates from millions of users, possibly using partitioning and load balancing.
• Data Storage: Store location history securely and ensure compliance with data protection regulations.

Learn More: Carrer Guidance

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