Everything you need to start as an engineer. In one place.
Notes on core CS concepts, DSA, LLD, design patterns and system design. Learn the topics. Use the tips to do well in interviews.
These are all my personal notes.
Browse the library
DSA: Python & Hacks
11 notes →CS Concepts
67 notes →OS FundamentalsProcesses, threads, locks, scheduling and memory — the OS basics.16OOPClasses, objects, inheritance and polymorphism, with Python examples.11SOLID PrinciplesThe five SOLID principles and how they show up in real code.7Design PatternsCreational, structural and behavioral patterns and when to reach for them.21LLDLow-level design walkthroughs: parking lots, elevators, rate limiters.12
System Design
38 notes →Getting StartedWhat system design is and how to think about it.1Networking EssentialsProtocols, load balancing, latency and the network stack.9API DesignREST, pagination, versioning, status codes and API security.5DatabasesStorage engines, indexing, ACID and isolation levels.9Data ModelingSchemas, keys, normalization and sharding for real workloads.7Caching & ScalingCaches and the techniques for scaling reads and writes.4Messaging & CoordinationQueues, gateways and distributed locks.3
Where I learned from
DSA
The best practice questions are on NeetCode. These notes help you get ready, or wrap up, right before an interview.
System Design
Hello Interview was my first path in, and the best place to start. These notes are my own, written while I learned, with extra deep dives into textbooks, search and Claude sessions.
Design Patterns
The patterns themselves come from the Gang of Four (GoF) book, Design Patterns: Elements of Reusable Object-Oriented Software. The explanations and examples here are my own.