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🖥 Interview Prep

CS Fundamentals

Big-O, memory, processes and threads, operating systems, networking, databases, security and OOP: the theory rounds.

📘 Learn it from scratch

Visual, hands-on lessons for every pattern in this topic. Do the lesson, then come back and the questions click.

Big-O in Plain EnglishMemory: The Stack, the Heap & ReferencesHow Numbers & Text Are StoredProcesses, Threads & Doing Things at OnceRace Conditions & How to Avoid ThemNetworking Deep Dive: DNS, TCP & HTTPSLatency Numbers & CachingInheritance vs CompositionSOLID Principles in Plain English

100 questions, most asked first

Ordered so the most useful questions for learning each pattern come first.

Any difficulty Easy Medium Hard

All patterns Complexity Processes & threads Memory Networking OOP SOLID & clean code Concurrency Operating systems Numbers & binary Security & crypto Design patterns Latency & caching Databases

Unlock 6 more CS Fundamentals questions · all 1,200 questions for $39/year (about 11¢ a day)See full access #35CPU caches and localityLatency & cachingHard🔒#45How databases store data on diskDatabasesHard🔒#47How databases execute joinsDatabasesHard🔒#57P, NP and NP-complete in plain EnglishComplexityHard🔒#70The dining philosophers problemConcurrencyHard🔒#88The two generals problemNetworkingHard🔒