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all posts →Core Concepts
Principles that are always true
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ML System Design
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Recently published
archive →Scaling Reads
Every lever for serving millions of reads per second — replicas, caches, fan-out, denormalization, CQRS — with case studies from Twitter, Netflix, and Discord.
Database Indexing
B-tree, LSM, hash, geospatial, inverted — which index to reach for, why, and the trade-offs an interviewer expects you to name. With SQL and production examples.
Networking Essentials
Networking for system-design interviews: layers, TCP/UDP, HTTP versions, REST vs gRPC, WebSocket/SSE, load balancing, CDN, and resilience. Diagrams + Go code.
#1 Two Sum — hash map in one pass [Easy]
One pass through the array, remember complements in a map. O(n) time, O(n) space.
Designing a graph-based payroll engine
How we modeled interdependent salary components as a DAG and used Kahn's topological sort to parallelize calculation across 6,000 employees in 30 seconds.