¶00 · About LLDCanvas
The LLD practice platform
built for the real round.
Low-Level Design — the machine coding round — is the interview that grades your thinking, not your syntax. LLDCanvas exists to make that thinking trainable: a full UML canvas, curated problems, timed practice, design pattern training, and eight applied challenge labs.
17
Features
110+
LLD Problems
8
Challenge Labs
12
Code Languages
¶01 · The Problem
Passive preparation does not build active design skills.
Low-Level Design is one of the most commonly failed interview rounds — not because developers don't know design patterns, but because they've never had to apply them under pressure on a blank canvas.
Reading a list of patterns is not preparation. Watching an explanation is not preparation. The real round gives you a problem statement, a ticking clock, and an empty whiteboard — and grades your thinking out loud.
LLDCanvas was built to close that gap: to give developers a complete, hands-on practice environment that mirrors the conditions of the actual interview rather than abstracting them away.
Traditional prep
- Memorising pattern names
- Passive reading / watching
- Isolated concept notes
- No timer, no pressure
- No design feedback loop
LLDCanvas approach
- Applying patterns on a real canvas
- Timed Interview Mode sessions
- Challenge Labs under real constraints
- Daily quiz for knowledge retention
- Immediate visual design feedback
What is a Low-Level Design interview?
Also called the machine coding round or OOD round — you design the internal classes, interfaces, and relationships of a real system (parking lot, ride-hailing, rate limiter) using UML notation, SOLID principles, and design patterns. It is a standard round at Amazon, Uber, Flipkart, Swiggy, and most product-based companies.
Browse 110+ LLD problems¶02 · Our Mission
Make Low-Level Design practice
interactive, structured, and accessible.
We believe every developer preparing for a technical interview should have access to a genuine practice environment — not just a list of questions — regardless of their background, experience level, or preparation timeline.
Build real design skills
Help developers develop genuine Low-Level Design and object-oriented design skills — not just memorised answers — that improve their everyday engineering work alongside their interview performance.
Practice in real conditions
Simulate the actual LLD interview environment — timed sessions, blank canvas, structured problem statements — so that the real round feels familiar, not foreign.
A complete ecosystem
Provide every tool in one place: the canvas to draw, the problems to solve, the notes to review, the labs to experiment in, and the roadmap to keep it structured.
¶03 · How We Approach Learning
One platform. Three interlocking ways to practice.
LLDCanvas brings together a complete learning ecosystem — not as isolated features, but as three complementary practice modes that build on each other. Draw, drill, and pressure-test your design thinking until it becomes instinct.
Canvas & Editor
Full UML class diagram canvas with 5 node types and 7 relationship types
ExploreDraft Notation
Write plain English — get a real UML diagram instantly
ExploreCode Execution
Run generated code in 12 languages, right in the browser
ExploreCollaboration
Live cursors, pinned comments, real-time shared canvas
ExploreInterview Mode
Timed sessions with streak tracking — the conditions of the real round
ExploreLLD Problems
110+ problems tagged by company, difficulty, and topic
ExploreRevision Notes
SOLID principles and all 23 GoF design patterns with analogies
ExploreDaily Quiz
10 pattern questions every day to keep knowledge sharp
ExplorePlannr
A sequenced roadmap from zero to interview-ready
ExplorePattern Detective
Read real code and identify the design pattern it uses
ExploreDebug Lab
Annotate design violations before the interviewer points them out
ExploreDebug & Fix
Restructure broken designs, not just identify what is wrong
ExploreLLD Roguelike
Procedurally generated, no-undo branching design scenarios
ExploreRefactor
Decompose a working monolith without breaking it
ExploreChange One Thing
Absorb a new requirement mid-design and adapt without full redesign
ExploreEvolution
Grow a design through multiple stages and track trade-offs
ExploreBudget Pressure
Make the best design decisions within real-world resource constraints
Explore¶04 · Who We Build For
From your first UML class diagram
to your most advanced LLD round.
LLDCanvas is designed around a spectrum — from developers drawing their first class diagram to senior engineers refining their design intuition under constraint.
Learning OOP, class diagrams, and design patterns for the first time. The canvas and revision notes offer a visual, hands-on starting point.
Targeting SDE-1 roles and placement interviews. Interview Mode and the problem library give you the structure and volume to build confidence.
Actively targeting SDE-2+ roles with a dedicated LLD round. The full platform — from Plannr through Challenge Labs — is built around your preparation loop.
Leveling up design thinking, exploring trade-offs, and sharpening architectural intuition. Evolution, Budget Pressure, and Refactor go beyond memorized answers.
Wherever you are in your journey, there's a practice mode built for it.
¶05 · Our Philosophy
The principles that shape every feature we build.
Learning by doing
Design skill is not absorbed through passive reading — it is built through repeated practice on real problems under real constraints. Every feature on LLDCanvas is built around active application, not passive consumption.
Understanding trade-offs
There is no single correct design. The goal is to understand why each choice has costs, and to be able to reason about them out loud. Features like Evolution, Change One Thing, and Budget Pressure make trade-off reasoning the practice.
Transferable engineering skills
Interview preparation that only produces interview answers is not enough. We want developers to walk away with stronger object-oriented design instincts that improve their actual engineering work — not just their ability to recall patterns under pressure.
Structured experimentation
Good design judgment develops through experimentation, failure, and reflection — not rote repetition of the same problem. The Challenge Labs are built to put you in novel, constrained situations you cannot solve by memorisation alone.
“The best preparation for an LLD interview is not reading about design patterns — it is applying them under pressure, making mistakes, and understanding why.”
LLDCanvas Platform Philosophy
¶06 · Looking Ahead
We're still building — and the direction is clear.
LLD preparation is not a solved problem. The gap between knowing a design pattern and applying it fluently under interview conditions is wide, and closing it requires more than a problem library.
Our focus is on making the practice more contextual, more adaptive, and closer to the real conditions of technical interviews at product-based companies. More challenge modes, more problem types, more ways to build and measure genuine design skill — not just interview familiarity.
Every new feature starts with the same question: does this make a developer measurably better at Low-Level Design, or does it just make the platform feel bigger?
¶07 · Ready to practice?
The best time to start
preparing is right now.
LLDCanvas is free to start. Open the canvas, work through a problem, run your design through Interview Mode — and see exactly where your preparation stands.