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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

Ranked by how often each question comes up in real interviews. #1 is the most common.

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🔒