Expertise
React expertise: fast, maintainable web interfaces
React is the reference JavaScript library for building component-based user interfaces. Version 19 introduces Server Components, Actions and the React Compiler, which simplify form handling, mutations and the elimination of unnecessary renders.
At Agencei, React is our foundation for rich web applications: admin panels, customer portals, dashboards and SaaS products. We always pair it with TypeScript, modern tooling (Vite or Next.js) and a testing strategy suited to the project.
This expertise is for companies that need a reliable interface that is quick to evolve, easy for a new developer to pick up, and able to absorb complex business logic without turning into technical debt over the years.
Use cases
Admin panels and internal tools
Management screens with filterable tables, complex forms and role-based permissions, built on reusable components.
SaaS products
Multi-tenant interfaces with onboarding, billing, notifications and polished loading states, designed to evolve over several years.
Real-time dashboards
Business data visualisation fed by WebSocket or SSE, with incremental updates and fine-grained client-side cache management.
Design systems
Documented (Storybook), accessible and themeable component libraries shared across several applications within the company.
Legacy interface redesigns
Progressive migration of a jQuery, AngularJS or server-rendered frontend to React, screen by screen, without service interruption.
Project types
- Business web application
- SaaS product interface
- Administration back office
- Customer portal or extranet
- Analytics dashboard
- Enterprise design system
Integration with the rest of the stack
React + Next.js
For sites and applications that need server rendering, file-based routing and strong SEO, we use React through Next.js and its App Router.
React + Spring Boot or Node.js API
The frontend consumes a typed REST or GraphQL API; OpenAPI schemas or shared types prevent drift between client and server.
React + TanStack Query
Cache management, background refetching and optimistic mutations, which drastically reduce hand-written state code.
React + AWS (S3, CloudFront, Amplify)
Static or hybrid deployment on AWS with a CDN, managed certificates and CI/CD pipelines that ship every branch to a staging environment.
Examples of problems solved
Unnecessary renders slowing down the UI
Profiling with React DevTools, component splitting, targeted memoisation or adopting the React Compiler to eliminate cascading re-renders.
Global state that became unmanageable
Replacing an oversized Redux store with a mix of context, TanStack Query for server data and Zustand for local state.
JavaScript bundle too heavy
Bundle analysis, route-level lazy loading with React.lazy and Suspense, removal of redundant dependencies.
Complex forms with inconsistent validation
Setting up React Hook Form with Zod schemas shared with the API, so validation is written once and runs on both client and server.
Frequently asked questions
Does React 19 change the way you develop?
Partly, yes. Actions simplify forms and mutations, the use hook lets you read promises and contexts, and the React Compiler automates most memoisation. The component model itself remains the same.
Should we use Next.js or plain React?
It depends on the need. An internal application behind authentication is often fine with React and Vite. A public site or a product that needs SEO and server rendering benefits from Next.js.
Do you use TypeScript on every React project?
Yes. Typing reduces regressions, documents components and makes refactoring easier. We also type API responses to keep client and server aligned.
How do you test a React application?
We combine component tests with Testing Library, unit tests on business logic with Vitest and end-to-end tests with Playwright on critical user journeys.
Can you take over an existing React application?
Yes. We start with an audit of the code, dependencies and performance, then propose a progressive recovery plan: version upgrades, removal of blockers and test stabilisation.
Related services
React development
High-performance web interfaces with React and Next.js, design systems and takeover of existing projects.
See this serviceWeb application
Business tools, portals and back offices built with React, Next.js, Node.js and Spring Boot.
See this serviceSaaS platform
Multi-tenant SaaS platforms with subscriptions, billing and infrastructure ready to scale.
See this serviceApplication redesign
Progressive modernization of ageing applications, with no business interruption or data loss.
See this serviceMobile app
Native or React Native apps for iOS and Android, from scoping to app store publication.
See this serviceWebsite development
Fast, well-ranked brochure and corporate websites built with Next.js, headless CMS or WordPress.
See this serviceRelated expertise
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