Sr Frontend Developer Jobs in Philadelphia, PA (NOW HIRING)

Senior Front-End Developer

Frontend Engineering

React TypeScript TanStack Router TanStack Query TanStack Form Tailwind CSS Vite

ABOUT THE ROLE

We are looking for a Senior Front-End Developer to join our engineering team and help build modern, scalable web applications that support business-critical workflows across the organisation. This is a hands-on engineering role for someone who enjoys building high-quality user experiences using React and TypeScript.

You will work across feature development, frontend architecture, API integration, performance optimisation, and platform improvements while collaborating closely with product managers, designers, backend engineers, and QA. You will be joining a mature codebase with established engineering standards, modern tooling, and well-defined architectural patterns.

We value engineers who take ownership, make thoughtful technical decisions, and care about building software that is reliable, easy to maintain, and enjoyable for other engineers to work in.

WHAT YOU'LL WORK ON

Build new product features using React, TypeScript, and the TanStack ecosystem.

Develop reusable, accessible UI components using a shared design system.

Integrate frontend applications with backend APIs and platform services.

Build and maintain complex forms, workflows, and data-driven user interfaces.

Improve application performance through code splitting, rendering optimisation, and modern React best practices.

Maintain and evolve frontend architecture while following established engineering conventions.

Improve accessibility, testing, observability, and overall developer experience.

Contribute to frontend tooling, CI/CD pipelines, and deployment processes where appropriate.

Collaborate with cross-functional teams to deliver high-quality software from design through production.

REQUIRED EXPERIENCE

React

Strong experience building large-scale applications using modern React.

Deep understanding of hooks, component composition, Context, Suspense, lazy loading, concurrent rendering, and rendering lifecycle.

Strong understanding of React performance optimisation, memoisation, and rendering behaviour.

Experience designing reusable component libraries and scalable frontend architectures.

Ability to reason about state ownership, derived state, effects, and component responsibilities.

TypeScript

Strong experience writing production applications in TypeScript.

Comfortable working with strict typing, discriminated unions, utility types, generics, and advanced type inference.

Experience using TypeScript to improve application design and developer experience.

TanStack Router

Experience building applications using nested routing, route loaders, search parameter validation, route

guards, and code splitting.

TanStack Query

Strong understanding of server-state management, caching, mutations, optimistic updates, invalidation strategies, and Suspense-first data fetching.

TanStack Form

Experience building complex forms with validation, dynamic fields, and schema-driven form management.

Zod

Experience building reusable validation schemas and leveraging type inference across APIs, routing, and forms.

STRONG TO HAVE

Tailwind CSS

Vite

Frontend performance optimisation

Accessibility (WCAG)

Modern authentication patterns (OAuth / OIDC)

Frontend observability tooling

Component-driven development

CI/CD pipelines

Infrastructure as Code

Experience working on large enterprise applications

HOW YOU THINK

You value maintainability over cleverness.

You understand when to introduce abstractions and when to keep solutions simple.

You write code that is easy for other engineers to understand and extend.

You think carefully about API design, component boundaries, and separation of concerns.

You understand the difference between local UI state, URL state, and server state, and choose the appropriate tool for each.

You leverage TypeScript as a design tool rather than simply a type checker.

You proactively identify opportunities to improve performance, accessibility, and developer experience.

You take ownership of the systems you build and consider long-term maintainability alongside feature delivery.

WHAT WE EXPLORE IN THE INTERVIEW

Strong candidates should be comfortable discussing:

React architecture and component design

Rendering behaviour and performance optimisation

State management strategies

Routing and data-fetching patterns

Building reusable component libraries

Type-safe application design using TypeScript

Designing maintainable frontend architectures

Trade-offs between different implementation approaches

Debugging and improving production applications

Collaboration, technical ownership, and engineering best practices

TECH STACK AT A GLANCE

UI Framework

React

Language

TypeScript

Routing

TanStack Router

Server State

TanStack Query

Forms

TanStack Form + Zod

Styling

Tailwind CSS + Shared Design System

Build

Vite

HTTP

Modern HTTP client

Authentication

OAuth / OIDC

Testing

Vitest

Observability

Frontend Observability Tooling

Infrastructure

AWS + Terraform + Serverless Framework