Temporary Full Stack React Developer Jobs in Denver, CO

Location: Remote or Hybrid (based on team needs)
Type of Role: Full-Time

We are looking for a Senior Full Stack Developer to join our growing international digital agency. The ideal candidate is an ambitious and driven modern JavaScript developer with a strong foundation in front‑end and back‑end development. While we specialize in HubSpot CMS and CRM development, prior HubSpot experience is not required—we are willing to train the right person.

This is a hands‑on, fast‑paced development role where you will build modern web applications, custom HubSpot solutions, and scalable backend systems. You will work closely with designers, strategists, and other developers to deliver high‑quality digital experiences.

Instrumental is a digital sales and marketing agency based in Golden, Colorado and a proud Elite HubSpot Partner. We help growth‑minded organizations build scalable, data‑driven marketing and revenue systems within the HubSpot ecosystem.

We operate with authenticity, craftsmanship, and a strong sense of ownership. We are not the loudest agency in the room, but we consistently earn trust through high‑quality work and measurable outcomes. Our team takes pride in building thoughtful systems and delivering meaningful client impact.

We have earned more HubSpot Impact Awards than any other agency because we stay focused on what matters most—delivering real results for clients. At Instrumental, strong culture and high standards go hand in hand.

We also embrace modern tools and workflows, including thoughtful use of AI, to improve speed, quality, and technical execution.

You are a strong digital professional who understands how great design supports user experience, marketing performance, and business outcomes.

You are confident collaborating across cross‑functional teams, translating strategy into thoughtful execution, and managing multiple priorities in a fast‑paced environment.

You are highly organized, detail‑oriented, and comfortable working under deadlines without compromising quality.

You are proactive, reliable, and take ownership of your work from concept through completion.

You are also curious about how modern tools and emerging technologies can improve your workflow, efficiency, and creative output.

AI is part of how modern teams do great work.

At Instrumental, we encourage thoughtful experimentation with AI tools to improve creative workflows, accelerate production, and enhance output quality. AI is used to support better thinking and faster execution, not replace design craft.

We expect team members to be comfortable engaging with AI as part of their everyday toolkit and to stay curious as the technology evolves.

• Build and maintain applications using React and Node.js
• Develop HubSpot CRM UI Extensions and interactive front‑end components
• Create serverless functions and custom‑coded workflow actions using Node.js
• Develop and maintain HubSpot CMS themes, templates, and modules (training provided if needed)
• Ensure high‑quality, performant, and accessible web experiences
• Work within project management tools (ClickUp, Jira, Asana, or Teamwork), Slack, and GitHub
• Collaborate with designers and strategists to translate requirements into technical solutions
• Stay current with modern web technologies and best practices

• 5+ years of professional full‑stack JavaScript development experience
• Strong proficiency in React.js and state management (Redux, Zustand, Context API, etc.)
• Solid experience with Node.js (Express, serverless functions, API development)
• Strong understanding of modern CSS (SCSS, Tailwind, CSS‑in‑JS, Grid, Flex, etc.)
• Experience working with APIs and data fetching (Axios or similar)
• Strong Git workflow experience (branches, pull requests, code reviews)
• Willingness to learn HubSpot CMS and CRM development

• Experience with HubSpot CMS and HubL
• Experience building HubSpot CRM UI Extensions
• Familiarity with GraphQL and REST APIs
• Experience with other CMS platforms (WordPress, etc.)
• Experience with backend languages (Python, PHP, Go, Elixir)
• Experience with databases (PostgreSQL, MongoDB, Firebase, Supabase, MySQL, Convex)
• Experience deploying apps to Vercel, Netlify, Render, or DigitalOcean
• Spanish fluency (a plus, not required)

• Comprehensive medical, dental, and vision insurance
• Short‑term and long‑term disability coverage
• Accident insurance for additional peace of mind
• 401(k) retirement plan
• 15 paid holidays plus generous PTO
• Quarterly incentive plan
• Collaborative, high‑performance team culture
• Award‑winning workplace recognized by Inc. and Great Place to Work

Instrumental is a growing international digital services agency helping clients across industries scale with HubSpot. As a leading implementation partner, we are trusted for both creative and technical execution. If you want to work with modern technologies in a fast‑paced agency environment, we want to talk to you.