Frontend Development: Design Systems, Rendering and Performance
How we build interfaces that stay fast and consistent: design tokens and component libraries, rendering chosen per route, performance budgets in CI and tested accessibility.
You want an interface that feels fast and predictable, matches the design down to the empty states, works with a keyboard and a screen reader, and stays easy to change after the hundredth feature. Frontend development is where product decisions become something people can touch, and where small shortcuts compound into slow, inconsistent screens.
Good frontend work has a recognizable shape: a shared component library instead of copied markup, a rendering strategy chosen per route rather than per trend, performance budgets that fail the build when they are exceeded, and accessibility tested like any other requirement.
What we build on the frontend
- Interfaces for SaaS products, customer portals and internal tools, often data-dense, with large tables, filters, charts and complex forms. Our overview of web application development shows how those products come together end to end.
- Design systems and component libraries shared across several products or teams.
- Fast marketing and content sites, where page weight shows up directly in search visibility and conversion.
- Rebuilds of legacy frontends, such as jQuery or AngularJS code nobody wants to touch, replaced screen by screen while the product stays live.
- Performance and accessibility rescues for existing applications.
We write TypeScript by default and work mainly with React, often through Next.js, and with Angular. The right choice depends on your team and product; the FAQ below touches on how we decide.
Design systems and component architecture
A design system starts with tokens: named values for color, spacing, typography, radius, elevation and motion, shared between the design files and the code. When the brand color or spacing scale changes, it changes in one place. Our UI/UX design team and our engineers maintain the tokens together, which closes most of the gap between the design file and the shipped screen.
Components are layered:
- Primitives such as buttons, inputs and checkboxes, with every state defined: hover, focus, disabled, loading and error.
- Composites such as date pickers, comboboxes, data tables and dialogs, usually built on accessible headless libraries (Radix or React Aria in React, the Angular CDK in Angular) rather than reinventing keyboard and focus behavior.
- Feature components that know your domain, organized by feature rather than by file type.
The library is documented in Storybook, with visual regression tests so a change to a shared component cannot silently break a dozen screens. Server data lives in a caching layer, such as TanStack Query in React or signal-based services in Angular, and local state stays local; a global store is reserved for state that really is global.
When several apps consume the library, it is published as a versioned package with a changelog, so each team upgrades deliberately instead of discovering changes in production.
One honest caveat: a full design system is overhead for a single small app. We start with tokens and the handful of components you need, and extract more as patterns repeat.
Choosing a rendering strategy: SSR, SSG or SPA
How HTML reaches the browser shapes speed, SEO, hosting cost and complexity. Modern frameworks let you choose per route, and most products need a mix.
| Strategy | Best for | Costs and caveats |
|---|---|---|
| Static generation (SSG) | Marketing pages, documentation, blogs | Content changes need a rebuild or incremental regeneration; unsuited to per-user content |
| Server-side rendering (SSR) | Public pages with fresh or personalized data, such as listings and search results | Needs servers and a caching strategy; the page still pays to hydrate in the browser |
| Single-page app (SPA) | Logged-in dashboards and tools where search indexing does not matter | Slower first load and bigger bundles; focus and scroll handling on route changes need deliberate work |
| Hybrid and islands | Mostly static pages with a few interactive parts | Framework-specific models, such as React Server Components or Astro islands, add concepts your team must learn |
A common and sensible split is a static marketing site in front of an SPA or SSR app behind login. What we avoid is shipping a large JavaScript bundle to render pages that are mostly text.
With SSR, caching decides the economics. Pages that look the same for every visitor can be cached at the CDN for seconds or minutes, which removes most of the server load, while personalized fragments load separately.
Performance budgets we actually enforce
A budget only works if something fails when you exceed it. We set per-route limits on JavaScript and total page weight, plus targets for the Core Web Vitals at the 75th percentile of real visits. Google’s thresholds for good are a Largest Contentful Paint of 2.5 seconds or less, an Interaction to Next Paint of 200 milliseconds or less, and a Cumulative Layout Shift of 0.1 or less.
Enforcement happens in three places:
- In CI: bundle size checks and Lighthouse runs on key pages under a throttled mobile profile, so a heavy dependency is caught in review rather than after release.
- In the code: route-level code splitting, lazy-loaded charts, editors and maps, virtualized long lists and tables, responsive images, and reserved space for anything that loads late.
- In production: real-user monitoring of the Core Web Vitals by page and device type, because lab scores on a developer laptop flatter everyone.
Most slow frontends are slow for dull reasons: too much JavaScript, unoptimized images, blocking third-party scripts and chatty API calls. We profile first and fix those before reaching for clever memoization.
Accessibility as an engineering practice
We target WCAG AA and treat it as part of the definition of done, not a final audit. In practice:
- Semantic HTML first. A real button beats a clickable div with ARIA bolted on, and incorrect ARIA is worse than none.
- Full keyboard support for custom widgets, following established patterns for menus, tabs, comboboxes and dialogs, including trapping focus inside a dialog and returning it when the dialog closes.
- Focus management on route changes in single-page apps, and live regions so screen reader users hear about toasts, validation errors and newly loaded results.
- Contrast checked at the token level, and animation that respects reduced-motion preferences.
Lint rules catch obvious mistakes while code is written, and automated axe checks run in component and end-to-end tests. Our QA testers then walk key flows with a keyboard and with screen readers such as VoiceOver and NVDA, because automated tools find only a portion of what real users run into.
How our frontend development engagements work
Frontend work rarely happens in isolation. We work from your designs or our own, against your API or one we build; our backend development guide covers that side.
Before building, we review designs for missing states such as loading, empty, error, long content and small screens, and agree on an API contract, usually OpenAPI with generated TypeScript types. Mocked endpoints let the interface move ahead while the backend is still in progress.
We build tokens and components first, then screens. Logic and component behavior are covered by unit and component tests, critical journeys by Playwright end-to-end tests, and QA testers check each iteration across browsers and devices. Releases go out behind feature flags, and real-user metrics guide what we improve next.
You get demos on a staging environment and regular written reports throughout. At the end you receive the application, a documented component library, automated tests, and a performance and accessibility report with the budgets wired into CI.
Frontend work alone is the wrong ask when the real problem is a slow API or a confusing product flow. If that is what we find, we will tell you where the time is actually going.
Frequently asked questions
React or Angular?
Both are solid. React offers a larger ecosystem and more freedom in how you structure an app; Angular gives large teams a consistent, batteries-included structure. Our Angular development guide explains when Angular is the better fit. Often your team’s existing skills decide it.
Will a single-page app hurt our SEO?
It can. Google renders JavaScript, but rendering happens in a separate, later step, and many other crawlers and link-preview bots do not run JavaScript at all. Pages that need to rank should be server-rendered or static.
Do we need a design system?
If you have more than one product, several frontend developers, or a brand that must stay consistent across many screens, yes. For a single small app, tokens and a core set of components are enough to begin.
Should we split our frontend into micro frontends?
Only when separate teams truly need to deploy parts of one interface independently. Otherwise, duplicated dependencies, inconsistent UX and harder integration testing outweigh the benefits, and a well-structured monorepo solves the same problem more cheaply.
Can you speed up our existing frontend?
Usually. We start from field data to find the pages and interactions that actually hurt users, fix the biggest causes first, then add budgets to CI so the gains do not erode.
If your interface feels slow, inconsistent or hard to change, tell us about your product and where your users struggle. We will start by looking at the real numbers.
