If you have 3+ years of experience and are starting to attend frontend interviews, you’ll quickly notice that Low-Level Design (LLD) is a common round. While it’s not always the most “critical” deciding factor like system design or algorithms, it’s often where interviewers separate a solid developer from a scalable-thinking developer.
What is LLD in Frontend?
In simple terms, LLD interviews focus on how you design and build UI components.
Think of components like:
- Accordion
- Star Rating Widget
- Tabs / Carousel
- File Explorer
- Modal with dynamic content
Yes, building them to “just work” is easy. But the real test is:
- Is your solution scalable?
- Is it optimised?
- Is it designed with the right pattern?
The Common Mistake Everyone Makes
Here’s what I’ve seen in interviews:
- Candidate gets the problem statement.
- Immediately jumps into code.
- Passes everything as props.
- Done.
Sure, it works. But as a senior, that’s not what the interviewer is looking for.
The real focus is patterns. Which one did you choose? Why? Is it extendable for future use cases?
Which Pattern Should You Use?
This is where many developers struggle. In regular day-to-day work, you might start with a simple props-driven solution and refactor later. That’s fine in real life.
But in a one-hour interview, picking the right pattern at the very beginning is crucial.
Patterns to Know (and When to Use Them)
1. Props-Driven Pattern
- When to use: For very small, straightforward components.
- Example: A Button that takes
variantandsizeas props. - Why it works: Simple and clean, but doesn’t scale well for complex components.
2. Higher-Order Components (HOC)
- When to use: When you need to wrap functionality around another component (logging, auth, feature toggling).
- Example:
withAuth(Component)for restricting access. - Why it works: Good for cross-cutting concerns, but less common with modern React (hooks/composition often preferred).
3. Render Props Pattern
- When to use: When you want to share logic but give flexibility in rendering.
- Example: A
<MouseTracker>component that passes coordinates to its children. - Why it works: Powerful, but can create “callback hell” if overused.
4. Component Composition Pattern ✅
- When to use: Almost always. Best for complex, reusable UI components.
- Example: Accordion →
<Accordion>with<Accordion.Item>,<Accordion.Header>,<Accordion.Body>. - Why it works: Clean, scalable, and mirrors how UI libraries (Radix, Material UI) build their components.
👉 Component composition pattern with React Context is one of my favorite patterns—it makes components even more powerful and flexible without prop-drilling.
👉 I’ve written a detailed post on Composition Pattern, check it out.
Learn from the Best: Reference Existing Libraries
Sometimes you build something and think it’s perfect. But the truth is—there are always multiple ways to approach a problem.
That’s why I recommend studying popular frontend libraries:
- Material UI
- Bootstrap
- Radix UI (my favorite!)
Radix powers shadcn, which is currently one of the cleanest, most scalable UI libraries. Reading their source will give you a real sense of interviewer expectations.
Extra Tips for Cracking LLD
- Talk before you code – Explain the approach, patterns, and trade-offs.
- Think scalability – Even if not asked, hint at how you’d extend the component.
- Handle edge cases – Empty state, loading state, accessibility.
- Keep it clean – Use meaningful naming and separation of concerns.
Final Thoughts
Frontend LLD interviews aren’t about whether you can code a dropdown. They’re about whether you can design scalable, maintainable, and extensible components.
So:
- Don’t just pass everything as props.
- Choose the right pattern from the start.
- Study how real UI libraries solve the same problems.
- Practice building small widgets with different approaches.
Once you internalize these habits, LLD interviews go from stressful to fun. And honestly, that’s when you’ll truly stand out as a senior React developer.
✨ Pro tip: Spend a weekend cloning 3–4 components from Radix UI or Shadcn. That practice alone will level up your LLD interview game.