Junior Full Stack Developer Jobs in Chelsea, MA (NOW HIRING)

Job Title: Full Stack Developer – React and Node.js

Location: (Boston/Springfield), MA

Duration: long term Contract

Senior Full Stack Software Engineer (React/TypeScript/Node.js)

Core 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.
• Contribute to technical design decisions: endpoint shape, permission resolution strategy, caching approach, component API design.

Required Skills and Experience

TypeScript and React (Non-Negotiable)

·       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/useCallback 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.

Node.js API Development

• 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.

Testing Discipline

• 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.

Communication and Collaboration

• Comfortable working from incomplete specifications. This codebase has documented open questions and known design ambiguities. You should be able to make reasonable implementation decisions while flagging assumptions clearly, rather than blocking on every undefined detail.
• Can write clearly about technical decisions — not lengthy documents, but precise comments, PR descriptions, and notes that explain why a non-obvious choice was made.
• Experience working in a two-week sprint cadence with regular demos and code review.

Typical Background

• 6–10 years of professional software development, with the last 3–5 years in senior or lead individual contributor roles on production web applications. Years are indicative, not a filter — the calibration above is what matters.