Top Full-Stack Engineer Jobs in Denver & Boulder, CO

Modernize a large fintech platform by building NestJS services and Next.js UIs, migrate transactional data to relational schemas, write comprehensive tests, identify and fix legacy problems, design scalable solutions that coexist with legacy systems, and use AI tooling responsibly to increase engineering velocity.

The Full Stack Engineer will develop features for a dynamic web application, collaborate with team members, enhance performance, and improve automated tests.

As a Fullstack Engineer, you'll design, build, and operate web applications, collaborating with product teams and mentoring peers while ensuring best practices in coding and system architecture.

Build and maintain FareHarbor.me, a managed WordPress site platform. Develop PHP and JavaScript features, craft themes/plugins and Gutenberg blocks, collaborate with design and product, review PRs, write docs, and improve accessibility, performance, and editor UX across thousands of client websites.

Build and own end-to-end full-stack features across backend services and user-facing applications. Contribute to system design, reliability, performance, observability, and engineering practices while collaborating with product and design.

The Software Engineer will design, maintain, and develop web solutions, focusing on real-time data and integrating geospatial data for front-end and back-end applications. Requires ownership of the software lifecycle, using modern frameworks and tools.

Lead the engineering effort for a seed-stage dating app: audit and improve the existing codebase, design and build v2 (mobile and backend), implement real-time features, define engineering standards, scale infrastructure on AWS, and, after fundraising, hire and mentor a small team while shaping the technical roadmap.

Lead architecture, modernization, and development of Group Insurance applications. Modernize mainframe monoliths into Java microservices and micro-frontends on cloud, mentor distributed Agile teams, collaborate with enterprise architecture, product owners and infrastructure, and enable test automation and integrations. Approximately 10% domestic travel.

The role involves leading application performance improvements across multiple platforms, focusing on measurable metrics and driving engineering standards and workflow optimization, using both hands-on coding and strategic influence.

Build and own Eve's marketing site and GTM engineering stack: integrate and optimize external tools, design AI agents for sales and marketing, implement webhooks and middleware to sync product/CRM data, and create programmatic campaigns and internal tools in partnership with Marketing, Sales, RevOps, and Product to drive growth and automation.

Lead frontend-leaning full-stack implementation work for carrier and enterprise integrations: architect reusable UI and API layers, author RFCs, guide technical delivery, enforce testing and security best practices, and partner with cross-functional teams to scope and ship production integrations.

Develop, maintain and evolve a high-scale US sports trading platform. Build React/TypeScript frontends, backend microservices, optimize SQL and performance, implement CI/CD and automated testing, mentor junior engineers, and collaborate with stakeholders and architecture teams to ensure resilience and integration.

As a Mid-Level Full Stack Developer, the role involves building and maintaining web applications, implementing new features, and optimizing performance using Ruby on Rails in a remote setting.

Lead full-stack mission engineer who designs, develops, integrates, and deploys software for DoD/IC missions. Lead cross-functional teams to build high-performance frontends and cohesive systems, collaborate with military customers for product discovery, and deploy and field-test solutions in secure operational environments (travel ~1 week/month).

Design, build, and maintain front-end visualizations and back-end web services for real-time geospatial data. Participate in full software lifecycle, ingest GIS/imagery data, improve tools/processes, and collaborate on modern web frameworks and performance profiling.

As a Senior Software Engineer, you'll design, develop, and maintain full-stack applications, utilizing TypeScript and modern frameworks while collaborating cross-functionally to enhance user experience and performance.

Seeking a full stack engineer to develop applications, requiring skills in Node.js, SQL, and modern JavaScript frameworks with a focus on scalability and performance.

Volunteer Principal Full Stack Engineer to lead and contribute across frontend and backend (React/React Native, Node.js, MongoDB). Own feature development, mentor engineers, collaborate with product/design, ship scalable code, and support CI processes. Must commit 4+ hours weekly and attend a weekly standup; first task includes launching a fundraising campaign.

Own end-to-end full‑stack features: design data models and clinical APIs, build backend services (TypeScript/Nest.js/Node.js on AWS), and implement React+TypeScript frontends. Deliver responsive clinical workflows, reimbursement integrations (MDS), FHIR extensions, EHR/vendor integrations, CI/CD, monitoring, and HIPAA/SOC2 readiness. Partner with clinicians, visit facilities, mentor hires, and iterate with product and design.

Senior .NET full-stack developer responsible for custom application development, API integrations, database optimization, deployments, troubleshooting, performance, security, and production support using .NET/C#, ASP.NET Core, SQL, modern frontend frameworks, cloud, and CI/CD.

As a Full Stack Engineer, you'll develop and maintain features, expand product lines, and explore AI applications in security infrastructure.

As a Founding Fullstack Engineer at MathGPT, you will build and ship modern web applications using React and Typescript, focusing on creating user-friendly and efficient products.

Build and ship end-to-end product features across frontend, backend, APIs and databases. Implement customer and internal workflows (onboarding, accounts, payments, rewards, FX, KYC, risk). Translate ambiguous product problems into reliable systems with clean UX. Collaborate with product, design, mobile and AI engineers. Create internal tools and automation, and own post-release monitoring, debugging and improvements.

Own end-to-end web application development: build responsive frontends, scalable backends and APIs, manage relational and NoSQL databases, implement cloud infrastructure and CI/CD, ensure performance, security, and accessibility while collaborating in Agile teams.

Design and build a high-performance, AI-native web trading experience for sophisticated retail traders. Ship core trading workflows (order entry, positions, blotter, watchlists, alerts), implement trustworthy AI UI patterns, collaborate with backend engineers on low-latency contracts, and iterate quickly with users and stakeholders to deliver end-to-end product features.