Opening low-level design
Progress is saved as you study.
12 pattern families, 46 lessons, about 36 hours of reading, and 8 families marked Interview Soon for the rounds that are close.
A low level design round hands you a small, concrete system — a parking lot, a vending machine, an elevator bank, a rate limiter — and asks for the classes: what the objects are, what each one owns, how they talk, and which parts you would let change later without rewriting the rest.
The answer is judged on object modelling rather than on scale. Interviewers look for clean responsibilities, the right design pattern applied for a stated reason instead of by reflex, thread safety where the problem needs it, and code that compiles in the language you claimed on your CV.
This course groups that skill into pattern families, from the OOP and SOLID foundations through the behavioural and creational patterns to concurrency and the timed machine-coding round. Each family is a page of its own listing the lessons it contains.
OOP pillars, SOLID principles, entity modeling and class extraction.
3 lessons · about 2.5 hours · Interview Soon
#1 and #4 most tested patterns: eliminate if/else chains with Strategy and create objects without specifying exact classes with Factory.
4 lessons · about 2 hours · Interview Soon
#2 most tested pattern: state transition tables, vending machine case study embedded.
3 lessons · about 2 hours · Interview Soon · 1 worked case study
#3 most tested pattern: Observer for event systems, Decorator for middleware chains, Command for undo/redo.
4 lessons · about 2 hours · Interview Soon · 1 worked case study
Race conditions, locks, BlockingQueue, thread pools, and pool sizing.
4 lessons · about 2 hours · Interview Soon
Three LLD round formats, time budgets, project structure, and pattern recognition.
2 lessons · about 1 hour · Interview Soon
Top 6 most-asked multi-pattern LLD problems: Parking Lot, Elevator, BookMyShow, Splitwise, Snake & Ladder, Rate Limiter.
6 lessons · about 5 hours · Interview Soon · 6 worked case studies
Advanced combos and data structure design: LRU Cache, Notification System, Chess, Food Delivery.
4 lessons · about 3 hours · Interview Soon · 4 worked case studies
Thread-safe designs, distributed patterns, and domain-heavy problems for SDE-2+ interviews.
8 lessons · about 8 hours · Deep Dive · 8 worked case studies
Financial systems, progressive design (Coinbase-style), and game engine patterns.
3 lessons · about 3 hours · Deep Dive
Company-specific machine coding prep and advanced architectural patterns.
2 lessons · about 2 hours · Deep Dive
Deep dives into Spring IoC, Java Collections, and Python data model internals.
3 lessons · about 3 hours · Deep Dive
Begin with the families marked Interview Soon. OOP foundations and class design come first because every later pattern is expressed in them, then the Strategy and Factory family, which covers the two patterns interviewers reach for most often.
Write the code, do not only read it. Lessons carry implementations in more than one language precisely so you can type the version you would use in the round and see where the abstraction starts to hurt.
Finish with the machine-coding family before an onsite. It is the one that rehearses the constraint that actually decides the round: a working, extensible design produced inside a fixed time box.
Interview Soon families: OOP Foundations & Class Design, Strategy & Factory Patterns, State Pattern & State Machines, Observer, Decorator & Behavioral, Concurrency Patterns, Machine Coding & Interview Execution, Case Studies — Foundational, Case Studies — Applied. Deep Dive families: Advanced Case Studies, Domain-Specific Patterns, Machine Coding Mastery, Architecture Teardowns.
