How to Approach an LLD Interview

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Applying SOLID and Composition in LLD Problems

See full structured answer at https://interviewexplainer.com/low-level-design-interview-questions/oo-design-with-solid-and-composition

Design a Parking Lot — Low-Level Design

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Design an Elevator System — Low-Level Design

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Design a Vending Machine — Low-Level Design

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Design Splitwise — Low-Level Design

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System Design·Interview Q&A

Low-Level Design (LLD) interview questions

7+ curated questions with the same answer shape every time: quick recap, deep dive, pitfalls, and follow-ups. Coverage includes lld fundamentals, parking lot, elevator system, vending machine, and more.

7questions

5topics

160difficulty

Open question 1 How to read this module

Suggested path

Read Low-Level Design (LLD) from question 1 to 7

Topics follow a teaching order. Each answer ends with a clear Next question control so you can move forward without hunting the list.

1Start with question 1 — it sets up the rest of the module.
2Use Continue · Next question at the bottom of every page (and the arrows in the sticky bar when you scroll).
3Jump to any topic in the full catalog — every row is numbered in reading order (Q1–Q7).

Open question 1 Jump to Q1 in list Scroll to full catalog

About this page

Low-level design (LLD) interviews test whether you can model a real system in classes. This module is an elevation arc: it opens with LLD fundamentals (identating classes, SOLID in design, the approach), then the classic interview problems in order of difficulty — parking lot, elevator system, vending machine, and splitwise. Each problem builds on the patterns of the previous one.

Reviewed by senior engineers·Updated for 2026·Free · No sign-up required

Part ofLow-Level Design (LLD)

High-signal Low-Level Design (LLD) questions

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Full catalog

Every question, in reading order

Topics are ordered for learning. Within each topic, rows are numbered 1–7 globally so you always know where you are. Collapse topics if you want a lighter view — use Expand all when you need the full list again.

Full catalog · reading order

Low-Level Design (LLD)

Numbers 1–7 follow the order we recommend — click any row to open the full answer, or use the sticky Next link at the bottom of each page to go Q1 → Q7.

7 questions·5 topics

All topics expanded

4Design a Parking Lot — Low-Level DesignMedium8m

5Design an Elevator System — Low-Level DesignMedium8m

6Design a Vending Machine — Low-Level DesignMedium8m

7Design Splitwise — Low-Level DesignMedium8m

Continue your prep

Interviewers rarely ask Low-Level Design (LLD) in isolation. These are the modules that most often come up in the same loop.

Most relevant next step18+ Q&A

Design Patterns & SOLID Interview Questions

Design-pattern interviews test whether you can apply a pattern to a real problem, not just name it. This module is an elevation arc: it opens with SOLID (the design-principle foundation), then the three GoF categories — creational, structural, behavioral — in order of how often they're asked. From there it moves to refactoring and technical debt (the applied tier: when patterns meet legacy code), then the legacy-patterns and comparison canon. It closes with scenario-based questions where you choose the right pattern for a stated problem.

Architecture Patterns & Principles

Also useful24

System Design Fundamentals

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FAQs about Low-Level Design (LLD) interview prep

QHow many Low-Level Design (LLD) interview questions are on this page?

This module bundles 7+ Low-Level Design (LLD) interview questions, grouped by 5 topics. Every answer follows the same structure — one-liner summary, structured deep-dive, common pitfalls, and realistic follow-ups an interviewer might ask.

QIs this Low-Level Design (LLD) content up to date for 2026?

Yes. Every answer is reviewed by senior engineers and updated for current best practices, version-specific APIs, and the scenario questions hiring managers are asking today.

QWhich difficulty level are these Low-Level Design (LLD) questions?

The set spans all three levels — 1 easy, 6 medium, and 0 hard questions. Junior candidates should focus on the conceptual questions; senior candidates should drill the scenario and trade-off questions in every topic group.

QWhich question should I read first?

Start with question 1 in the ordered list below ("Low-Level Design Fundamentals") — it is the recommended entry point. Then use the Next question link at the bottom of each answer page to read straight through to Q7.

QWhat else belongs in a Low-Level Design (LLD) prep plan?

Low-Level Design (LLD) is one module inside the broader Low-Level Design (LLD) hub — open it to drill the full set of sibling modules with the same structured answer format.

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