Practice real LLD & System Design
interviews.
AI-powered interview simulations for backend engineers and software developers. Code in a real workspace, get a senior-staff review, ship better designs.
No credit card · 10 free practice sessions
interface PricingStrategy {
price(spot: Spot, hours: number): number;
}
class HourlyPricing implements PricingStrategy {
price(spot, hours) {
return spot.tier.rate * hours;
}
}
class ParkingLot {
constructor(
private floors: Floor[],
private pricing: PricingStrategy,
) {}
assign(vehicle: Vehicle): Ticket { /* ... */ }
}Built for engineers
Everything you need to design like a staff engineer.
A focused, opinionated toolchain. No tabs across five apps — practice, review, and progress in one premium workspace.
VSCode-grade workspace
Multi-file Monaco editor with file tree, tabs, and dark theme tuned for design problems.
AI as interviewer, not judge
Get follow-ups, tradeoff prompts, and senior-engineer commentary — not pass/fail.
Pattern detection
Strategy, Factory, Observer — your code is reviewed for design pattern fit and misuse.
Version-aware submissions
Every attempt is preserved. Compare evolutions of the same design over time.
Interview readiness score
A composite of solved depth, pattern coverage, and review quality. Trend it weekly.
Guided learning paths
SOLID → patterns → architecture. Each lesson cross-links to practice problems.
How it works
A workflow shaped by real interviews.
Four steps. No fluff. Every interaction is designed to mirror how a senior engineer thinks through a design problem.
- No artificial pass/fail
- Tradeoff-first feedback
- Real interviewer pacing
- 01
Pick a problem
From Parking Lot to Food Delivery — 50+ curated LLD problems with company tags.
- 02
Design in workspace
Multi-file Monaco editor. Models, services, interfaces — your choice.
- 03
Get reviewed
AI reviewer evaluates modularity, SOLID, patterns, and asks follow-up questions.
- 04
Iterate & track
Compare submissions over time. Watch your interview readiness score climb.
Loved by engineers
From candidates who shipped offers.
"Finally, an interview prep that doesn't grade me like a compiler. The AI's follow-ups felt eerily close to my Stripe loop."
"I run mocks on loopIQ before every onsite. The tradeoff prompts forced me to actually defend my designs."
"Cleared L5 LLD in two weeks. The Parking Lot review caught coupling I'd ignored for months."
Pricing
Premium tools, honest pricing.
Free
Get a feel for the workspace.
- 10 practice sessions/mo
- 5 AI reviews/mo
- Learning hub access
- Community leaderboards
Pro
Most popularFor active interview prep.
- Unlimited practice
- Unlimited AI reviews
- Mock interview simulator
- Pattern detection
- Submission compare
Team
For bootcamps and orgs.
- Everything in Pro
- Team leaderboards
- Custom problem sets
- SSO & SAML
- Analytics dashboards
FAQ
Questions, answered.
Your next design round, already practiced.
Join thousands of engineers using loopIQ to ship sharper designs and walk into interviews with reps in the bank.