Day 29SWE · OOPS & SOLID
Encapsulation, inheritance, polymorphism, abstraction
- • Walk through the four pillars of OOP with code examples.
- • When does composition beat inheritance?
Ship code under pressure
Python, SQL, and Coding Foundations
Build the implementation speed and data fluency needed for coding, SQL, and ML-from-scratch rounds.
Featured topics
3 topic cards built for interview prep
Each topic includes a summary, practical learning goals, representative interview prompts, and a suggested roadmap day.
Intermediate120 minDay 20
ML Coding From Scratch
Implement classic algorithms from first principles to sharpen your understanding and whiteboard fluency.
Learning objectives
- • Write linear and logistic regression without relying on framework abstractions
- • Explain the update rule and convergence behavior of simple optimizers
Intermediate90 minDay 23
SQL Window Functions
Solve ranking, funnels, retention, and cohort prompts with clean analytical SQL.
Learning objectives
- • Choose between joins, CTEs, and windows for readability and performance
- • Implement ranking, rolling aggregates, and funnel analysis
Beginner75 minDay 78
Python Interview Patterns
Review Python language features that regularly appear in ML interview coding rounds.
Learning objectives
- • Use iterators, generators, and comprehensions to write concise solutions
- • Explain typing, exceptions, and common pitfalls in production Python
Practice prompts
Daily-plan topics tied directly to this pillar
These are pulled from the same 133-day roadmap content used by Browse Questions.
Day 29SWE · OOPS & SOLID
SOLID: SRP, OCP, LSP, ISP, DIP
- • Walk through each SOLID principle with a real example.
- • Which SOLID principle do you violate most often, and why?
Day 29SWE · OOPS & SOLID
Common OO design mistakes (god class, anemic models, deep inheritance)
- • Spot a god class — what would you refactor it into?
- • Why are deep inheritance hierarchies usually a smell, and what do you reach for instead?
Day 30SWE · Design patterns
Creational: factory, builder, singleton
- • When is a singleton an anti-pattern in tests?
- • Compare factory vs abstract factory vs builder.
Day 30SWE · Design patterns
Structural: adapter, decorator, facade
- • When would you reach for an adapter vs a facade?
- • Where does the decorator pattern show up cleanly in an ML inference pipeline?
Day 30SWE · Design patterns
Behavioral: strategy, observer, command
- • Show how the strategy pattern lets you swap ML models without touching call sites.
- • When does observer cause subtle bugs in a high-throughput system?
Day 31SWE · Concurrency in Python
Python GIL — what it does and doesn't lock
- • Explain the GIL and why threading helps I/O-bound but not CPU-bound work in CPython.
- • When does multiprocessing beat threading for ML workloads?
Day 31SWE · Concurrency in Python
asyncio: event loop, coroutines, gather
- • When is asyncio the right choice over threads/processes?
- • What are common pitfalls with mixing sync and async code?