Basics 1

Question 1

What is a URL shortener?

Answer 1

A service that converts long URLs into shorter, fixed-length URLs that redirect to the original address.

Question 2

What are the advantages of a URL shortener?

Answer 2

Improves readability, saves space, enables easy sharing, and can include tracking analytics.

Question 3

What are the disadvantages of a URL shortener?

Answer 3

Adds a redirection layer, introduces dependency on the shortener service, and may pose security risks if abused.

Question 4

What are best practices when designing a URL shortener?

Answer 4

Use a scalable key generation algorithm, avoid collisions, use caching for redirects, implement rate limiting, and support custom aliases.

Question 5

What are common use cases for a URL shortener?

Answer 5

Social media posts, marketing campaigns, QR codes, and analytics tracking for links.

Question 6

How does a URL shortener impact system design?

Answer 6

Requires considerations around performance, availability, storage, key generation, analytics, and abuse prevention.

Question 7

Give an example of a URL shortening service.

Answer 7

Bitly, TinyURL, or Google’s deprecated goo.gl are well-known examples.

Question 8

What are the architectural components of a URL shortener?

Answer 8

Typically includes an API layer, key generator, database (for mappings), redirect handler, cache layer, and monitoring/analytics pipeline.

Question 9

What are common key generation strategies?

Answer 9

Auto-incrementing IDs encoded in base62, UUIDs, or hash-based methods to ensure uniqueness and efficiency.

Question 10

How can performance be ensured in a URL shortener?

Answer 10

Use caching (e.g., Redis) for frequently accessed URLs, CDN for static redirection, and minimize DB lookups.

Question 11

How can fault tolerance be added to a URL shortener?

Answer 11

Use redundant database replicas, load balancers, and retries; decouple components via message queues where needed.

Question 12

How is monitoring and debugging handled in a URL shortener?

Answer 12

Track redirect latency, cache hit/miss rates, request volume, and error rates; use logs and distributed tracing.

Question 13

What is a real-world tradeoff in a URL shortener?

Answer 13

Short keys improve UX but may increase collision risk; long keys reduce collisions but impact usability.

Question 14

What is a common interview question on URL shorteners?

Answer 14

Design a scalable URL shortener—how would you handle unique key generation and redirects at scale?

Question 15

What is a potential gotcha in URL shorteners?

Answer 15

Lack of abuse detection can lead to phishing/malware links; also, poor key design may cause collisions or non-uniqueness.

Question 16

What is Pastebin?

Answer 16

A web application where users can store plain text, such as code snippets or logs, for sharing via unique URLs.

Question 17

What are the advantages of Pastebin?

Answer 17

Simplifies sharing of text/code, provides version control, and allows for public or private pastes.

Question 18

What are the disadvantages of Pastebin?

Answer 18

Potential for misuse (e.g., sharing sensitive data), and may require moderation to prevent abuse.

Question 19

What are best practices when designing Pastebin?

Answer 19

Implement user authentication, content moderation, expiration times for pastes, and syntax highlighting for code.

Question 20

What are common use cases for Pastebin?

Answer 20

Sharing code snippets, logs, or configuration files among developers or support teams.

Question 21

How does Pastebin impact system design?

Answer 21

Requires efficient storage for text data, search functionality, and mechanisms for content expiration and privacy settings.

Question 22

Give an example of a Pastebin service.

Answer 22

Pastebin.com is a popular example of such a service.

Question 23

What are the architectural components of Pastebin?

Answer 23

Includes a web interface, database for storing pastes, user authentication system, and optional features like syntax highlighting.

Question 24

How can performance be ensured in Pastebin?

Answer 24

Use caching for frequently accessed pastes, optimize database queries, and implement pagination for listing pastes.

Question 25

How can fault tolerance be added to Pastebin?

Answer 25

Deploy redundant servers, use database replication, and implement regular backups.

Question 26

How is monitoring and debugging handled in Pastebin?

Answer 26

Monitor server performance, track user activity, and log errors for debugging.

Question 27

What is a real-world tradeoff in Pastebin?

Answer 27

Balancing user anonymity with the need for moderation to prevent misuse.

Question 28

What is a common interview question on Pastebin?

Answer 28

Design a Pastebin-like service—how would you handle storage, retrieval, and expiration of pastes?

Question 29

What is a potential gotcha in Pastebin?

Answer 29

Failing to sanitize user input can lead to security vulnerabilities like XSS attacks.

Question 30

What is a rate limiter?

Answer 30

A mechanism that controls the rate of incoming requests to prevent overloading a system or abuse.

Question 31

What are the advantages of a rate limiter?

Answer 31

Protects services from abuse, ensures fair usage, and helps maintain system performance.

Question 32

What are the disadvantages of a rate limiter?

Answer 32

May inadvertently block legitimate users if not configured properly.

Question 33

What are best practices when designing a rate limiter?

Answer 33

Implement per-user limits, use sliding window algorithms, and provide informative error messages.

Question 34

What are common use cases for a rate limiter?

Answer 34

API request limiting, login attempt restrictions, and controlling traffic to services.

Question 35

How does a rate limiter impact system design?

Answer 35

Requires tracking request counts, managing state (possibly distributed), and ensuring low-latency enforcement.

Question 36

Give an example of a rate limiter in action.

Answer 36

An API that allows 100 requests per minute per user, returning a 429 error when exceeded.

Question 37

What are common algorithms used in rate limiting?

Answer 37

Token Bucket, Leaky Bucket, Fixed Window, and Sliding Window algorithms.

Question 38

How can performance be ensured in a rate limiter?

Answer 38

Use in-memory data stores like Redis for tracking, and optimize algorithms for low latency.

Question 39

How can fault tolerance be added to a rate limiter?

Answer 39

Implement distributed rate limiting with consistent hashing and fallback mechanisms.

Question 40

How is monitoring and debugging handled in a rate limiter?

Answer 40

Track metrics like request counts, blocked requests, and latency; log anomalies for analysis.

Question 41

What is a real-world tradeoff in rate limiting?

Answer 41

Strict limits protect services but may hinder user experience; lenient limits may allow abuse.

Question 42

What is a common interview question on rate limiting?

Answer 42

Design a rate limiter for an API—how would you handle distributed enforcement and fairness?

Question 43

What is a potential gotcha in rate limiting?

Answer 43

Improper synchronization in distributed systems can lead to inconsistent enforcement.

Question 44

What is a file storage service like Dropbox?

Answer 44

A cloud-based service that allows users to store, sync, and share files across devices.

Question 45

What are the advantages of a file storage service?

Answer 45

Provides data accessibility, backup, collaboration features, and scalability.

Question 46

What are the disadvantages of a file storage service?

Answer 46

Requires robust security measures and can be complex to implement synchronization.

Question 47

What are best practices when designing a file storage service?

Answer 47

Use chunking for large files, implement deduplication, and ensure secure data transfer and storage.

Question 48

What are common use cases for a file storage service?

Answer 48

Personal file backup, team collaboration, and document sharing.

Question 49

How does a file storage service impact system design?

Answer 49

Necessitates handling large volumes of data, ensuring data consistency, and providing high availability.

Question 50

Give an example of a file storage service.

Answer 50

Dropbox, Google Drive, and OneDrive are popular examples.

Question 51

What are the architectural components of a file storage service?

Answer 51

Includes client applications, metadata servers, storage servers, and synchronization mechanisms.

Question 52

How can performance be ensured in a file storage service?

Answer 52

Implement CDN for file delivery, optimize synchronization protocols, and use efficient storage solutions.

Question 53

How can fault tolerance be added to a file storage service?

Answer 53

Use data replication, distributed storage systems, and implement disaster recovery plans.

Question 54

How is monitoring and debugging handled in a file storage service?

Answer 54

Monitor storage usage, sync errors, and system health; provide logs for troubleshooting.

Question 55

What is a real-world tradeoff in file storage services?

Answer 55

Balancing storage costs with redundancy and performance requirements.

Question 56

What is a common interview question on file storage services?

Answer 56

Design a Dropbox-like service—how would you handle file synchronization and conflict resolution?

Question 57

What is a potential gotcha in file storage services?

Answer 57

Handling file version conflicts and ensuring data consistency across devices.