Grokking the Object Oriented Design Interview

The round people prepare for last

Object oriented design sits between coding and system design, and it gets skipped in many preparation plans. Then a candidate who can solve hard graph problems is asked to design a parking lot and spends forty minutes talking without structure. At many companies this round appears as "low level design" or "machine coding", especially for mid-level roles.

What it covers

The course page lists 6 chapters, 49 lessons, 156 playgrounds and about 35 hours of study time (September 2026).

• Introduction: what the course covers, a complete answer in five minutes, and a study plan.
• Object oriented design and UML: OO basics, analysis and design, and the four diagrams worth drawing at a whiteboard (use case, class, activity, sequence).
• How to answer an OOD question: how the interview runs, turning a one-line prompt into requirements, finding the classes, choosing relationships (association, aggregation, composition, inheritance), keeping the design honest with SOLID, and the design patterns that come up in this round.
• 22 case studies, grouped with an assessment after each group:
  • Everyday objects: parking lot, library, ATM, elevator, vending machine
  • Booking and inventory: movie tickets, hotel, car rental, restaurant, airline
  • Games: blackjack and chess
  • Platforms: Stack Overflow, Cricinfo, LinkedIn, Facebook, Amazon, a stock brokerage
  • Pattern-driven components: Splitwise, a notification service, an in-memory cache, ride sharing
• Final exam.

Every case study goes from requirements to diagrams to a complete implementation in Python, Java and C++.

Is it worth it?

As of September 2026 the course page lists a one-time price of $75 for lifetime access, and it is included in the provider's all-courses subscription. It shows a 4.2 rating from about 10,900 ratings and roughly 60,700 learners.

The course's strength is a single method applied consistently across 22 problems, with diagrams and working code for each, so the approach becomes automatic rather than something you improvise.

How long it really takes

Plan two to three weeks at an hour or two a day. If time is short, do the method chapter, then five or six from different groups (parking lot, elevator, movie booking, chess, Splitwise, in-memory cache is a good spread).

How to use it well

• Do the requirements step out loud, on a timer, before reading each solution. The first five to ten minutes is much of what is being assessed.
• Draw the class diagram yourself first, then compare. Focus on where your responsibilities differ from the solution's.
• Write the core classes in your interview language for at least three case studies. Many companies expect running code in a machine coding round.
• Learn a handful of patterns properly (strategy, observer, factory, singleton, state) rather than trying to name every pattern.

Best for: candidates at companies with a dedicated object oriented or low level design round, and anyone whose interviews include a machine coding stage.