Senior React Developer Jobs in Amherst, MA (NOW HIRING)

Job Summary:
eTeam is seeking a Senior Full Stack Developer with expertise in React and Node.js. The role involves building full vertical slices of products, designing shared components, and participating in sprint planning, while ensuring high-quality code through testing and documentation.
Responsibilities:
• Build and own full vertical slices of the product: React components, TypeScript interfaces, RTK Query endpoints, Node.js/Express handlers, etc. within the same feature.
• Design shared component and API patterns that other stories consume — not just implementing your own tickets but considering how the building blocks you create will be used across the feature.
• Participate actively in sprint planning and backlog refinement; push back on stories that lack sufficient design or data specification before they enter a sprint.
• Write behavioral tests (Vitest React Testing Library) alongside implementation, not as a separate phase.
• Identify and document reuse opportunities across implementation areas — patterns and observations that prevent duplicate work by teammates.
Qualifications:
Required:
• 5 years of professional React development; 3 years using TypeScript in a production React codebase — not just annotating JS, but designing typed data contracts, discriminated unions, and generic component interfaces. Strong understanding of React 18 patterns: functional components, custom hooks, memo/use Callback usage, Suspense and lazy loading.
• Practical experience with Redux Toolkit and RTK Query: defining API slices, managing loading/error states, understanding caching and cache invalidation behavior. Experience with Redux middleware or Thunks is useful but secondary to RTK Query fluency.
• Form handling with react-hook-form and schema-based validation (Yup or Zod). Comfort with multi-step forms, conditional field logic, and controlled vs. uncontrolled patterns. Familiarity with design system libraries coupled with the ability to read component documentation and use the provided components correctly without reaching for custom solutions.
• 3 years building and maintaining REST APIs with Node.js and Express (or equivalent framework).
• The ability to design endpoint shapes that are efficient to consume from the client and that handle partial failures gracefully.
• Experience integrating with external APIs or SaaS platforms — writing against third-party REST or SOAP interfaces, handling pagination, rate limiting, and API version differences.
• Working knowledge of authentication middleware: JWT validation, token refresh patterns, understanding of OAuth 2.0 / OIDC flows even if you have not built them from scratch.
• Comfort with Redis for caching: setting TTLs, invalidation strategies, understanding when caching introduces staleness risk.
• Writes tests as part of implementation, not after. Can articulate the difference between testing behavior and testing implementation details.
• Experience with React Testing Library (or equivalent) — tests that simulate user interactions and assert on visible output, not on component internals.
• Able to write meaningful tests for async behavior (loading states, API responses, error boundaries) using mocked service layers.
Preferred:
• Configuration-Driven UI Patterns
• Authentication and Identity
• Event-Driven Systems -Exposure to Apache Kafka or a comparable message broker — consuming events from a topic, understanding at-least-once delivery, schema registry basics.
• Financial Services Domain
• Python API Development- Production experience building REST APIs in Python using FastAPI, Flask, or Django REST Framework. Data Manipulation and ETLm-Hands-on experience using Python for data transformation work.
• Accessibility-Working knowledge of WCAG 2.1 AA compliance — aria attributes, keyboard navigation, screen reader behavior.
Company:
eTeam is a staffing agency that also provides payrolling services. Founded in 1999, the company is headquartered in Somerset, USA, with a team of 501-1000 employees. The company is currently Late Stage.