CrackingWalnuts
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41problems
System Design Interview Playbook
40-min walkthroughs with grading by level, follow-up Q&A, and one-pitch cheat sheets across every problem.
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90problems
Low-Level Design Interview Playbook
45-min code-in-sequence walkthroughs, whiteboard diagram mode, and grading rubric on every problem.
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145topics
Concurrency Section
Mental models, lock-free patterns, real-world bugs, and runnable examples in Go, Java, and Python.
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Pattern Pick
Merge Intervals
DSA TemplateIntermediate
ExploreDesign Blueprint
Airbnb
Low Level DesignIntermediate
ExploreScale Study
Design an Ad Exchange / RTB Platform
System DesignHard
Deep divePacket Probe
TCP Deep Dive
Networking & ProtocolsIntermediate
ExploreStaff+ Prep
Migration Planning Interviews
Staff+ InterviewExpert
ExploreKernel Dive
Heap Allocators (malloc internals)
Linux InternalsAdvanced
Deep dive
System Design: Maps Platform (Navigation, Routing, and Map Rendering)
Design a maps platform serving 1B daily users with real-time routing, tile rendering, traffic overlays, and offline navigation.
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System Design··79 min
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DSA Templates
50Algorithm patterns & code templates
System Design
41End-to-end architecture problems
Low Level Design
90Design patterns & practical code
Key Technologies
59Deep dives into core tech
Infrastructure
35Production systems & operations
Networking & Protocols
51TCP, HTTP, TLS, DNS & more
Concurrency
145Threads, channels, async, locks in Java + Python + Go
Distributed Systems
38Consensus, replication & more
Linux Internals
84Kernel, networking & system calls
Cheat Sheets
24Quick reference cards for interviews
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27Interactive Tools
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Elixir / BEAM
The runtime that handles millions of concurrent connections where Java and Go need hundreds of servers
Database Sharding
Horizontally partitions data across multiple database instances using a shard key
CRUSH: Topology-Aware Data Placement
CRUSH replaces the question 'where IS my data?' with 'where SHOULD my data be?' Any node can compute the answer locally using the same algorithm and cluster map, with no central placement database and no network call