Sam, a passionate frontend developer, had been in the job market for what felt like forever.
Applications? Sent.
Portfolios? Polished.
LinkedIn DMs? Ignored.
After months of trying, when burnout started to creep in, his phone buzzed with an unexpected call.
“Hi Sam, this is Eva from SELTA Technologies, a leading US product company. We loved your portfolio and would like to invite you for an interview next week!”
Sam was thrilled. Elated. Finally, a breakthrough!
The recruiter walked him through the interview process:
- Coding round
- UI implementation
- Behavioral round
- System Design round
Wait... System Design? Sam blinked.
Yes, we have a System Design round that focuses on frontend systems.
A cold shiver ran down his spine.
System Design? For the frontend? That’s for backend folks, right? Microservices? Load balancers? Kafka?
Sam had never prepared for that. HTML, CSS, React hooks? Sure. But frontend System Design? What even is that?
Panic crept in. Questions swirled:
What do they expect?
Will they ask me to draw architecture diagrams?
Do I talk about Redux? React Query? Tailwind?
Sam felt like he’d opened the right door, only to find a trapdoor underneath.
But little did he know, he wasn’t alone.
Thousands of engineers like him had felt the same jolt: the realization that building interfaces was no longer enough. Interviews were changing, expectations were shifting, and System Design had entered the frontend world.
That’s when Sam stumbled on something different.
In his case, it was this blog (at least). And for you, it is too.
So, let’s rewind, zoom out, and discuss what frontend System Design means and how engineers like Sam (and you) can master it before your next big interview.
Let’s dive in.
What is frontend System Design?
Modern frontend applications are dynamic, deeply interactive, and often more complex than the backend systems they sit on. A single product dashboard might manage real-time data streams, permission layers, undo histories, and animations, all in the browser.
Take a typical e-commerce interface: it’s expected to handle infinite scrolling product lists, real-time cart updates, offline browsing support, personalized recommendations, accessibility compliance, secure payment integrations, and seamless responsiveness across devices. This level of complexity can’t be managed by simply building a UI. It demands a proper system that’s thoughtfully architected, fault-tolerant, and designed to scale.
Frontend System Design is the discipline of planning and architecting a cohesive, maintainable, and resilient UI system to work, scale, perform, and evolve as needed.
It’s about answering hard questions before they become bottlenecks:
- Why is this drop-down so slow on mobile?
- Why does fixing one bug break something else?
- Why does adding a feature take so long?
Frontend System Design is how we fix that.
Note: Want to master Frontend System Design and confidently tackle interviews? Check out the Grokking the Frontend System Design Interview course, it’s built to help you deeply understand frontend System Design principles and design scalable, real-world frontend architectures with clarity.
Why does frontend System Design matter?
Not long ago, most system complexity sat neatly on the server. The frontend rendered whatever the backend handed down. Pages were assembled with templating engines, refreshed on each click, and followed a linear flow. In that world, System Design belonged logically to backend engineers.
Imagine building an online storefront. It’s no longer a few product pages and a static cart. It now should support the features, as illustrated below:
Note: In the frontend context, SDKs are pre-packaged libraries or toolkits provided by third parties (like Stripe, Firebase, Google Analytics, etc.) that developers integrate into their applications to quickly enable features such as payments, authentication, analytics, or chat, without building everything from scratch.
One person rarely builds a large-scale application. Today’s frontend systems involve dozens of engineers across multiple teams, each owning different verticals. You might have a team owning checkout, another on the search experience, another maintaining the design system, and another managing real-time promotions.
And here’s the catch: these teams don’t work in isolation. Their work intersects. A shared drop-down component used in both the cart and the account settings might have subtle differences that lead to regressions. A change in how the product list fetches data could impact performance metrics across the site.
In these environments, a lack of system thinking causes real harm, not just to code, but to collaboration. Architecture decisions now affect how teams deploy, integrate, test, and roll out features.
Here’s a consolidated overview of why frontend System Design matters more than ever:
- Performance: Slow, unresponsive interfaces degrade user experience and diminish engagement. A button that responds within 200ms feels immediate and satisfying, while one that takes 800ms or more feels broken.
Frontend System Design gives us the tools: virtualization, debouncing, lazy loading, and chunk splitting, to make interfaces fast and feel fast.
- Maintainability: Without a well-structured foundation, every new feature introduces risk. Without clear boundaries, developers face duplicated logic, regressions, and fragile UIs that are increasingly difficult to evolve.
A good System Design enforces boundaries, reusability, and predictability so teams can move faster without fear.
- Scalability: Backend systems scale with infrastructure, load balancers, caching layers, and service meshes. However, frontend systems scale through architecture. For organizations maintaining large-scale products like Gmail, Notion, or Figma, scaling the UI means enabling hundreds of developers to work in parallel without creating chaos.
Without a scalable frontend system, these apps would be impossible to maintain across hundreds of contributors.
Frontend is the user experience. This is what the user touches. This is the product. We can have the best backend in the world, but if our frontend stutters, freezes, or crashes, our product feels broken.
Why does it show up in interviews?
When Sam received an interview call, he didn’t expect System Design to come up. For years, frontend developers were spared that round, because System Design was someone else’s job.
But the industry has changed. Quietly, but dramatically.
As discussed earlier, the way companies build products has evolved, and so has the role of the frontend engineer. So when a company asks a frontend developer to walk through a System Design round, it’s not because they want to trip you up with backend trivia. They’re looking for signals:
- Can you give a reason for the state flow and ownership?
- Can you define boundaries that allow other teams to work safely?
- Can you identify potential bottlenecks before they ship to users?
It’s no longer enough to know what to build. You’re expected to know how it should evolve, how it scales, and where it might break. Without thoughtful System Design, frontend code becomes a brittle mess full of hacks, regression, and unpredictable behavior.
This makes a great frontend engineer in 2025, not just one who renders components but designs cohesive systems under constraints.
A comparison of a thoughtful frontend System Design with a poorly developed system is illustrated below:
Understanding why Frontend System Design matters is just the beginning, but it doesn’t yet tell you how to design one. So let’s get practical.
What does it look like to architect a frontend system? How do you go from vague requirements to clear component structures, data flows, and performance safeguards? And how do you design not just for what works, but for what lasts?
The following section will summarize the mindset, principles, and framework guiding thoughtful frontend System Design.
How to design frontend systems
Designing a frontend system is part craft, part engineering. It requires balancing user experience, code maintainability, team scalability, and performance. To do this effectively, we need a structured approach.
We’ll cover this in two layers:
- Core principles: We’ll discuss the principles that guide system thinking in frontend.
- REDCAAP framework: We’ll explore a step-by-step design methodology to apply those principles in practice.
Let’s start with the foundational ideas.
Core principles of frontend System Design
These principles are like compasses. They won’t give you all the answers, but they’ll help you ask the right questions, especially under constraints like team size, performance demands, or tight deadlines:
- Component architecture: We should break the interface into small, composable units that reflect business concepts. Leverage patterns such as atomic design or feature-first folder structures.
Example: In a shopping cart app, you might have: , , , , etc. Each of these should do one thing and do it well. Don’t mix responsibilities.
- State management: The State is what makes frontend systems complex. We can use local state for isolated logic (like form inputs), global state for shared data (like logged-in user), and server state when fetching remote data.
- Smart vs. dumb components: We should split components by responsibility. Let smart (container) components handle logic and state (fetch data, perform logic, dispatch actions); dumb (presentational) components should focus on rendering (Receive props, render UI).
- Performance optimization: We should consider techniques like lazy loading, virtualization, memoization, and event throttling to help scale our UI to handle large datasets and real-time interactions.
Example: For a chat app with thousands of messages, rendering all at once will tank performance. Virtualization helps by only rendering what’s visible.
- Monitoring and observability: Frontend issues are often invisible without tooling. We should integrate performance monitoring (Web Vitals, Lighthouse), logging (Sentry, LogRocket), and analytics tools to gain feedback loops.
Example: A real-time dashboard shows data with a delay. Is it network latency or rendering jank? Monitoring tools can pinpoint the bottleneck.
- Platform responsiveness: We should handle responsiveness across screen sizes, browsers, and network conditions. We should use flex layouts and media queries, handle offline and slow network states, and consider accessibility.
Example: Your newsfeed UI might look great on a desktop, but test it on a 375px-wide phone, and see how quickly assumptions break.
After exploring the core principles to use while designing a frontend system, it is equally important to have a blueprint to architect the system strategically. Let’s explore that.
The REDCAAP framework
While principles guide our thinking, the REDCAAP framework provides a structured process for applying them. This framework is beneficial when designing systems for complex applications, such as an e-commerce platform.
Here’s an overview of the steps included in the framework:
Let’s walk through each phase of REDCAAP with examples grounded in a real-world scenario: building an e-commerce storefront.
- Requirements (R): Every design starts with constraints and expectations. The first task is identifying what the system must do and how well it must do it.
For an e-commerce platform, this might include allowing users to browse, search, and checkout seamlessly, even on low-bandwidth connections. We might also need real-time stock updates or offline cart syncing.
- Design patterns and architecture (D): Once requirements are clear, the next step is selecting patterns that define structure and flow.
Do you use MVVM to isolate view logic?
MVI for strict state transitions?
Will this be a monolithic SPA or a micro-frontend platform with independently deployed verticals?
In a large-scale commerce site, search, checkout, and order history might each be owned by separate teams. Choosing the correct design pattern here directly affects stability and velocity across the system.
- Components and hierarchy (C): Frontend systems are built from reusable parts. This step focuses on identifying and organizing those parts in a clear hierarchy.
A product page, for instance, might break down into ImageGallery, PriceTag, AddToCartButton, and ReviewList.
- Architecture (A): This step defines how frontend modules are structured and how they interact with backend services. Good architecture ensures that the UI is not just a set of components, but a coordinated system.
For example, in an e-commerce app, the cart, product detail, and checkout modules should operate independently, yet integrate smoothly through shared APIs and state layers.
- API design (A): A well-designed API enables the frontend to retrieve just the right data quickly and predictably. This step focuses on crafting endpoints and data models that serve the UI efficiently.
For instance, we can use structured, purpose-driven endpoints like:
- /products?category=shoes&limit=20
- /products/:id/reviews
- /cart/items
This minimizes overfetching, supports modular UI components, and keeps the app fast and scalable.
- Performance optimization (P): The system should feel fast. In this step, we anticipate bottlenecks and design the frontend to be fast, inclusive, secure, and globally adaptable.
For example, in an e-commerce app, using responsive image loading (< img srcset > with device breakpoints) ensures faster product rendering on both mobile and desktop, without sacrificing quality or speed.
With this framework in mind, it’s crucial to understand what you need to consider at each stage while designing real-world frontend systems. Let’s discuss this.
Real-world frontend design considerations
Frontend System Design becomes truly valuable when applied to real product scenarios. In these moments, when requirements get messy, timelines shrink, and trade-offs emerge, design thinking separates resilient applications from fragile ones. Consider you’re building a modern e-commerce platform:
Do you virtualize the product list? On mobile, rendering 1,000+ product cards can tank performance. Virtualization ensures only visible elements are rendered at any moment.
How do you cache product data for offline access? Should product detail pages be available when the user loses connectivity? What’s the expiration policy for cached data?
Do you debounce search inputs? A search box that triggers API calls on every keystroke leads to wasted bandwidth and server load. A 300ms debounce can drastically reduce noise.
Should you optimistically update the UI after adding it to the cart? Waiting for the API response adds perceived latency. A well-designed optimistic update shows the item in the cart immediately and handles failure gracefully in the background.
How do you isolate failures from third-party services like payment widgets or review plugins? Sandboxing, fallback UIs, and feature flags help maintain stability when external scripts fail.
These are not edge cases. They are everyday realities of building modern frontend systems. Frontend System Design gives engineers a proactive framework to handle them before they become bottlenecks.
Sam was shocked, but you shouldn’t be. It’s time to be prepared upfront; the foremost thing to do is shift your mindset.
Mindset shift: From code to systems
At the heart of frontend System Design lies a shift in how engineers think, not just about what they’re building, but also how it will grow, scale, and survive change.
Most developers begin with a code-first mindset: What’s the best way to implement this component? But great frontend engineers adopt a system-first mindset: What’s the best way to design this so others can build on top of it, without breaking it?
Rather than focusing on the present feature alone, system-first thinking anticipates future needs, team collaboration, and architectural stability. The right question isn’t just “Does this work now?”, it’s:
- Will this component (e.g., ProductCard) adapt to new business use cases like bundles or subscriptions without rework?
- Can this architecture support dozens of engineers contributing across a shared surface without stepping on each other?
- What happens when usage spikes or network conditions degrade? Does the system degrade gracefully?
This is the difference between tactical coding and architectural thinking. System Design helps engineers anticipate the future and build with it in mind.
Final thoughts
Most frontend engineers start by learning how to make things work, such as center a div, render a list, and connect a button to an API.
But the next level? It’s not about writing more code, it’s about designing smarter systems. Systems that:
- Evolve without collapsing.
- Empower teams, not trap them.
- Deliver delight at scale, not just locally.
Frontend System Design is about architecting those systems. It’s about seeing beyond the component before you and understanding how your decisions today shape the user experience, team efficiency, and product resilience tomorrow.
Still wondering what they’ll ask in that System Design round?
Our “Grokking the Frontend System Design Interview” course is built for engineers like you who can create beautiful interfaces but want to design systems that last. You don’t need to guess what great design looks like. You just need the right lens, and we built it for you. And next time, when the recruiter says: There’s a frontend System Design round, you won’t flinch. You’ll say, Perfect. I’m good with that.
Top comments (1)
Hi Fahim, thank you for posting this. The discussion around frontend systems was much needed. Your article fulfils the need to understand system design from a frontend perspective and how to approach a design problem with a structured approach.