Low level design interview practice
You don't fail the LLD round on design. You fail it on requirements.
Given a problem statement — a parking lot, a splitwise, a locker system — most candidates skim it and jump to classes. Interviewers probe: "where did that requirement come from?" LLDrill is a 7-minute drill that forces you to read like an interviewer before you design like an engineer.
Free account · 1 free AI review · 4 classic problems · paste your own
- Statement →
- you skimmed it in 30 seconds
- "payment" →
- a noun to you, a hidden pay feature to them
- "several rooms" →
- a collection someone owns — did you ask who?
- "for now" →
- a design decision left open — did you notice?
- Score →
- 0/10
Why a requirements drill exists
In most LLD interview questions, half the requirements are stated plainly and half are hidden — inside nouns, counting words, and phrases like "for now". Candidates who skip extraction design the wrong thing confidently.
Six fast passes: verbs, nouns, seven questions per feature, rules and future words, three buckets, then testable Given/When/Then sentences. The same routine senior engineers run in their heads — made visible.
A hint-free AI interviewer cross-examines your answers and scores you out of 10 — coverage, clarifying questions, edge cases, testability, communication. Practice until the verdict says ready.
What the drill trains
Every pass runs against the 7-minute timer. By the end, each of your requirements is sourced, owned and testable.
Every verb is a feature — and nouns like 'notification' hide verbs like 'notify'. You list the stated ones and hunt the hidden ones.
Counting words ('several rooms', 'each user') mean a collection — and something owns it. You spot them before they become table mistakes.
One row per feature, seven fixed questions: who does it, on what, what goes in, what must be true first, what changes, what can go wrong, who must know.
'Must not exceed', 'for now', 'later' — rule words need an owner, future words mean the design stays open. You record which is which.
Everything becomes a Requirement, a Question, or an Assumption. Nothing stays vague. The mock interviewer answers what the statement hides.
Each requirement is rewritten as Given / When / Then. If you can't imagine the test, it isn't a requirement yet.
How it works
- 1. Pick or paste a problem
Start with a classic — Meeting Room Scheduler, Parking Lot, Splitwise, Elevator — or paste the exact statement from your last interview.
- 2. Run the six passes in 7 minutes
Click words straight out of the statement, answer the seven questions, and push every unknown into a bucket or an assumption. A readiness check tells you when you're ready for entities.
- 3. Get interviewed and scored
The AI interviewer reads your P1–P6 work, asks follow-ups without giving hints, then scores you out of 10 with strengths, gaps and a verdict.
What you get out of it
- Find hidden features before the interviewer points at them
- Ask clarifying questions that sound senior, not scripted
- Turn vague statements into Given/When/Then testable requirements
- Catch rules ('max 8 hours', 'no same-day slots') and give each one an owner
- Practise under the same clock the real interview gives you
- Track your score across drills and watch it climb past 80
Simple pricing
Drills are free. Pay only when you want the AI interviewer.
All six passes, the mock interviewer and the readiness check. Free account required.
One full AI interview with a score out of 10. First review on every new account is free.
15 AI interviews over 7 days ($7), or 45 every month ($15), plus exports.
Frequently asked
What is low-level design (LLD) in an interview?
An LLD round gives you a short problem statement — a parking lot, a splitwise, a locker system — and asks you to design the classes, relationships and logic. What most candidates underestimate is that the first phase is requirements gathering: extracting features, rules and edge cases from the statement before drawing anything.
Why do candidates fail the requirements phase?
They read the statement once and start coding. They miss hidden features buried in nouns, never ask about scale or expiry rules, and leave requirements untestable. The interviewer sees a design with no trace of why it looks that way.
Do I need an account to practice?
Yes — a free account is required. It keeps your drills, history and AI scores synced across devices, and every new account gets one free AI review.
What does the AI interviewer do?
It reads everything you produced in the six passes, then interviews you like a real LLD interviewer — probing questions only, no hints, no answers. When you finish, it scores you out of 10 with strengths, gaps and a verdict on whether you're ready to move to entities.
Your next LLD round starts with the statement.
Run one drill today. You'll never read a problem statement the same way again.
Start a 7-minute drill