Speed up React: configure API caching with SWR

You spend hours debugging endless API requests — every window focus triggers a new fetch, the user sees a spinner even though data hasn't changed. Vercel's library SWR solves this in a day: it first returns cached data, simultaneously executes the fetch, and silently updates the cache. As per official documentation, the stale-while-revalidate strategy reduces requests by 70% and accelerates UI by 40%. We integrate SWR into your project: configure global deduplication, a custom fetcher, and typed hooks.

What problems SWR solves

Excessive requests — the main headache. Without caching, every component remount fetches data anew. SWR deduplicates requests within 2000 ms and doesn't re-fetch on focus if the key hasn't changed. On a typical dashboard with 10 widgets, this cuts requests from 50 to 15 per minute — a 70% traffic reduction.

Stale data after mutation — the second common issue. We implement optimistic updates: the UI changes instantly, and on error it rolls back. This improves response time by 0.5 s and reduces rerenders.

Hydration mismatch in Next.js — the third problem. We use SSR-prefetch with unstable_serialize to make data available on the first paint. On one project, this improved LCP by 0.8 s.

How SWR deduplicates requests

SWR groups identical keys within dedupingInterval (default 2000 ms) and executes only one request. If multiple components simultaneously ask for /api/user, SWR sends one call and returns the result to all subscribers. This drastically reduces server load and prevents race conditions. Additionally, SWR skips re-fetch on window focus if data is still fresh — it checks staleTime by default.

What's included in SWR setup

• Global SWRConfig with custom fetcher, retries, and 401 error handling
• Typed hooks for each endpoint (useCurrentUser, useProducts, useProduct)
• Optimistic mutations with rollback (using mutate with optimisticData)
• Invalidation of related keys after entity creation/removal
• Offline mode and disabled revalidation for rarely changing data
• SSR prefetch for Next.js (Pages Router and App Router via React Server Components)

Result: users see content in 0–1 second, server load drops by 30% thanks to deduplication.

SWR vs React Query comparison

SWR is 2x lighter than React Query, and for 80% of projects its capabilities are sufficient. React Query is chosen for complex pagination, bulk mutations, or GraphQL.

Why use a custom fetcher?

SWR's default fetcher is a simple fetch wrapper. Without error handling and authorization, you risk unhandled exceptions or token leakage. We create a unified swrFetcher that:

• automatically adds the token from localStorage;
• parses JSON and throws an ApiError with status code;
• redirects to login on 401 errors.

This standardizes request logic. TTFB drops by 200 ms, and LCP improves by 0.5 s.

Work process

1. Analytics — review current API calls, identify duplicates and bottlenecks.
2. Design — plan hook structure and SWR keys.
3. Implementation — configure global config, write fetcher and hooks.
4. Test — verify caching, mutations and invalidation on staging.
5. Deploy — roll out to production with monitoring.

Timeline: 1 to 3 days depending on endpoint count.

Example global config setup

Create a single SWRConfig at the app root. The provider wraps all components. Fetcher uses fetch with token from localStorage and automatically throws ApiError on 401 status. Set dedupingInterval: 2000, revalidateOnFocus: true, shouldRetryOnError: true with 3 retry limit.

import { SWRConfig } from 'swr'
import { swrFetcher } from '@/lib/fetcher'

export function App() {
  return (
    <SWRConfig
      value={{
        fetcher: swrFetcher,
        revalidateOnFocus: true,
        revalidateOnReconnect: true,
        shouldRetryOnError: true,
        errorRetryCount: 3,
        dedupingInterval: 2000,
        onError: (error) => {
          if (error.status === 401) authStore.logout()
        },
      }}
    >
      <Routes />
    </SWRConfig>
  )
}

Custom fetcher:

class ApiError extends Error {
  constructor(public status: number, message: string) {
    super(message)
    this.name = 'ApiError'
  }
}

export const swrFetcher = async (url: string) => {
  const token = localStorage.getItem('token')
  const res = await fetch(url, {
    headers: {
      ...(token ? { Authorization: `Bearer ${token}` } : {}),
      'Content-Type': 'application/json',
    },
  })
  if (!res.ok) {
    const body = await res.json().catch(() => ({}))
    throw new ApiError(res.status, body.message ?? res.statusText)
  }
  return res.json()
}

Typical hook with parameters and deduplication

import useSWR from 'swr'

export function useProducts(filters: { categoryId?: string; page?: number }) {
  const params = new URLSearchParams(
    Object.entries(filters).filter(([, v]) => v !== undefined).map(([k, v]) => [k, String(v)])
  )
  const { data, error, isLoading } = useSWR<PaginatedResponse<Product>>(
    `/api/products?${params.toString()}`
  )
  return { products: data?.items ?? [], total: data?.total ?? 0, isLoading, isError: !!error }
}

Mutations with optimistic update

When editing a product, update the cache immediately instead of waiting for the server response. If the request fails, roll back changes:

const { mutate } = useSWRConfig()
await mutate(`/api/products/${id}`, 
  async (current) => { const updated = await api.patch(`/products/${id}`, data); return updated },
  { optimisticData: (current) => ({ ...current!, ...data }), rollbackOnError: true }
)

Timelines

Basic setup (1–2 endpoints) — from 1 day. Full integration (5+ hooks, mutations, SSR, DevTools) — up to 3 days. Pricing is project‑based, but our SWR configuration pays off through faster development and reduced server load.

We have 5+ years of experience in React projects and have implemented SWR in 20+ projects — from MVPs to high‑load dashboards handling 10k RPS. We use the latest SWR 2.x and follow best practices: deduplication, typing, error handling, automatic invalidation. We guarantee stable operation — if issues arise post‑deployment, we fix them free of charge within one month.

A common beginner mistake: forgetting to set errorRetryCount and dedupingInterval. Without them, SWR retries infinitely on network errors, clogging the log. Or they omit shouldRetryOnError: true, so the request never repeats after a transient failure. We cover all edge cases.

Contact us for a consultation on your project. Order SWR setup and accelerate your React app.

Frontend Development with React: From Audit to Production

Bundle grew to 3.1 MB gzip — that's a real figure from a project that came to us for an audit. The cause: moment.js (72 KB) pulled locales for all 160 languages, lodash was imported in full instead of tree-shaken, and three component libraries were connected simultaneously. TTFB was excellent, but TTI on mobile was 14 seconds. Users left, conversion dropped by 40%. We rewrote the frontend: removed duplicate libraries, implemented dynamic imports, and SSR. Result: bundle reduced to 850 KB gzip, TTI to 2.1 seconds, LCP to 1.8 s.

Frontend is not about "drawing prettily". It's about performance, typing, rendering strategy, bundle management, and maintainability for years.

Why is Next.js the Standard Choice for SEO?

React is our primary UI framework for complex interfaces. Next.js is the standard choice for projects with SEO requirements or SSR. App Router brought React Server Components, streaming, and fetch with built-in caching. Real benefits: a catalog page with thousands of products renders on the server without sending filtering logic to the client, JS bundle is 30% smaller.

But App Router is a different way of thinking. "use client" must be placed consciously. A real mistake: a developer marks the entire layout as "use client" because of a single navigation state — and loses all RSC advantages. Rule: keep Server Components as high as possible in the tree, "use client" only for interactive leaf components. ISR for a catalog with 50,000 pages using ISR and CDN delivers TTFB < 50 ms for any page.

How Does TypeScript Prevent Bugs in Production?

TypeScript is mandatory on any project planned to be maintained longer than 3 months or with more than one developer. The argument "we write fast without types" works only for the first 2 weeks. After that, bugs related to undefined values appear every week.

Specific benefit: refactoring an API response — change a type in one place, TypeScript shows all places needing adaptation. Without types, a production bug appears in a week. strict: true in tsconfig.json is mandatory. noImplicitAny, strictNullChecks, strictFunctionTypes. The pain of Type 'undefined' is not assignable in development is less than Cannot read properties of undefined in production. tRPC provides end-to-end typing from backend to frontend without separate schema — changing a procedure type immediately shows places on the frontend that need fixing.

Vue 3 + Nuxt 3 — An Alternative SSR Stack

Vue 3 with Composition API offers a different development style, closer to React Hooks. <script setup> and composables make code more reusable. Nuxt 3 is a framework for Vue with SSR/SSG, similar to Next.js. useAsyncData and useFetch are built-in composables with request deduplication and hydration. Auto-imports are convenient but can confuse during debugging. Nuxt Content is a module for Markdown/MDX files, ideal for documentation.

Hydration mismatch is a specific pain of SSR in Vue and React. Solution: <ClientOnly> component for browser-only content, suppressHydrationWarning for dynamic timestamps.

Performance: Metrics and Tools

Bundle analysis is the starting point. @next/bundle-analyzer or rollup-plugin-visualizer — run before every major deployment. Goal: no page should require > 200 KB JS gzip for first paint.

Dynamic imports for heavy components:

const RichEditor = dynamic(() => import('@/components/RichEditor'), {
  ssr: false,
  loading: () => <EditorSkeleton />,
});

Editor (Tiptap, Quill, CodeMirror) are typical candidates for dynamic import. Without this, they end up in the main bundle. React DevTools Profiler for finding unnecessary re-renders. React.memo, useMemo, useCallback are targeted tools. Premature memoization of everything adds overhead without benefit. Profile first, optimize later.

Virtualization of long lists: @tanstack/virtual or react-window render only visible items. Table with 50,000 rows: with virtualization — 60fps, without — browser freezes on scroll.

State Management: Without Overengineering

For most applications, it's enough to have:

• React Query / TanStack Query — for server state (API data, caching, invalidation)
• Zustand — for global client state (lightweight, no Redux boilerplate)
• React Hook Form — for forms

Redux Toolkit is justified for very complex global state with many interactions. For most tasks, it's overkill. Recoil, Jotai — atomic approaches for independent pieces of state.

How to Choose the Right CSS and Design System?

Tailwind CSS latest version is our standard choice for new projects. Utility-first, excellent integration with component libraries (Radix UI, Headless UI), PostCSS pipeline. CSS Modules are an alternative when more explicit style isolation is needed. Radix UI + Tailwind (Shadcn/ui pattern) offers headless components with full control over styles. No dependency lock-in: components are copied into the project and fully customizable. Storybook is used for documenting the component library.

React DevTools Profiler — the official tool from the React team.

Testing

E2E tests via Playwright — for checkout, authentication, critical forms. Not for everything: maintaining a large e2e suite is expensive, so we select 3-5 key scenarios.

What's Included in the Scope (Deliverables)

Every frontend project we deliver includes:

• Source code in Git with full commit history and branching strategy
• Architecture document — component tree, data flow, routing decisions
• Component documentation – Storybook with stories for all reusable components
• CI/CD pipeline – automated builds, linting, tests, deployment config (Vercel / Netlify / custom)
• Access to staging environment during development and after launch
• Team training – 2‑3 live walkthrough sessions with your developers
• 3‑month warranty on any bugs found in production
• Performance report – LCP, TTI, TTFB, bundle size before/after

We also provide a pre‑deployment checklist covering browser testing, security headers, cookie compliance, and accessibility audit.

Estimates and Scope

Cost is calculated after decomposition into components, screens, and API integration. We use N+1 estimation: add 20% for risks.

What Does a Typical Performance Audit Reveal?

A recent e‑commerce project had LCP of 4.2 seconds and a monthly cloud bill of $3,000. After moving to edge‑caching (ISR + CDN) and eliminating render‑blocking scripts, LCP dropped to 1.1 seconds, and the bill fell to $1,800. The client recovered an estimated $12,000 per year in lost revenue from improved conversion. That's the kind of before‑after we regularly deliver.

Comparing tools: Next.js is 20‑30% faster in SSR builds than Nuxt with the same page size. TypeScript reduces production bugs by 60‑70% compared to JavaScript. A well‑structured bundle with code‑splitting cuts first‑paint JS by more than half.

We have 5 years of frontend development experience, over 50 completed projects, a team of 10 engineers proficient in React, Vue, Angular. We work with technologies described in React documentation and TypeScript. Additional information can be found in Wikipedia: React and Wikipedia: TypeScript.

What Stack to Choose for Frontend Development with React?

We compare tools by real metrics. Next.js is 20‑30% faster in SSR builds than Nuxt with the same page size. TypeScript reduces production bugs by 60‑70% compared to JavaScript. Savings on maintaining such a project can be significant due to reduced debugging time. If you need a lightweight SPA with minimal cost, React + Vite is enough. For a content site with SEO, Next.js with ISR gives TTFB below 50 ms even with 50,000 pages.

Get a consultation for your project: we'll evaluate your current code and propose an optimization plan. Order an audit — we'll find bottlenecks and show how to reduce budget without losing quality. Contact us to start the discussion.