Case Study Index: Design Classics, Grouped by Theme
You'll learn to
- -Know which remaining HLD levels group into which real-world themes
Between the module chapters and the five worked examples you just read, this course has now bridged a chapter to a specific level about twenty-five times, and the HLD Lab has 70 levels. Everything beyond the levels already linked is capstone territory: applying the whole toolbox at once, with less hand-holding about which concept applies where. Here's a map of what's left, grouped by theme rather than listed in order.
Interview Classics
The systems most frequently asked about in real interviews, each combining several modules from this course at once: Photo Sharing (Level 16), Payment System (Level 21), Distributed Message Queue (Level 22), Team Messaging (Level 31), and Email Service (Level 40).
Staff-Level & Advanced Systems
Systems with a genuinely hard core problem, not just more scale: Stock Exchange Order Book (Level 28), Object Storage / S3 Clone (Level 33), Code Repository (Level 35), Maps & Navigation (Level 39), Video Conferencing (Level 45), and Auction System (Level 47).
The Second Pass
Levels 55 through 59 deliberately revisit five systems from earlier in the lab (Ride-Sharing, Video Streaming, Real-Time Messaging, Collaborative Editing, and a Distributed Task Scheduler) this time at Expert and Master difficulty, expecting the full toolbox this course has built rather than the beginner's version of the same problem.
Planet-Scale Systems
The Grandmaster and Master tier levels are where every module in this course shows up in one design at once: Global Stock Exchange (Level 60), Multi-Tenant SaaS Platform (Level 61), Global Payment Processing (Level 63), Distributed Tracing Platform (Level 64), Distributed Search Engine at Google scale (Level 67), Multi-Region Active-Active Database (Level 68), and Real-Time Fraud Detection (Level 69).
GenAI-Flavored Systems
Levels 50 through 54 apply this same system-design toolbox to AI infrastructure specifically: a RAG Pipeline, a Vector Search Engine, an AI Gateway, a Real-Time Recommendation Engine, and an Autonomous Agent Platform. If these interest you, ScaleDojo's GenAI lab track goes considerably deeper.
There's no required order here: pick whichever theme matches what you're preparing for, and treat the 5-step loop from the previous chapter as your starting point for every one of them.
What do Levels 55-59 represent in the HLD Lab?
Level 70: The Final Boss is the capstone of the entire HLD Lab - a global-scale social platform that expects every module in this course at once.