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.

Lead design, build, and deploy full-stack software for DoD/IC missions. Rapidly prototype MVPs, integrate systems and APIs, deliver high-performance frontends, collaborate with users, and deploy/test in secure operational environments.

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.

The Full-Stack Engineer will build and maintain applications, own features end-to-end, contribute to system design, and collaborate closely with product and design teams while improving system reliability and performance.

Build and grow Homebot applications, services, and APIs end-to-end. Use AI tooling to rapidly deliver features, create AI-driven workflows, and ship maintainable, well-tested, scalable code. Collaborate with product, design, and engineering, and instrument systems with monitoring, logging, tracing, and analytics.

Secure customer-facing products, APIs, and internal services through threat modeling, architecture and code reviews. Remediate vulnerabilities by coding fixes in Python/Go/JS/TS. Build and manage SAST/DAST/SCA security pipelines in CI/CD. Configure WAFs, API gateways, and bot protection. Provide secure coding guidance, run bug bounty triage, and support compliance (SOC 2, ISO 27001, GDPR).

Develop fullstack web applications, enhance platform performance, collaborate on high-impact opportunities, and ensure stable, scalable solutions. Engage in rapid iterations and be a committed team player.

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.

As a Senior Fullstack Engineer, you'll contribute to backend development for Toast's New Ventures team, collaborating on architecture and launching MVPs while addressing unmet operator needs.

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.

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.

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.

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.

As a Senior Software Engineer in ZT1, you will lead backend system development, manage projects, and influence product direction in a fast-paced, AI-centric environment.

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.

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.

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.

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.

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.

Build end-to-end full-stack AI features on a Ruby on Rails backend and React frontend, design and run experiments (A/B tests and AI evaluations), implement AI infrastructure for reliable LLM inference, and iterate quickly to scale production-ready LLM-powered products.

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.

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

As a Staff Full Stack Engineer, you will develop and maintain web applications, collaborate with teams, ensure scalability, and provide technical leadership. You will work with APIs and user interfaces to enhance patient data accessibility in healthcare.

Hands-on SAP ABAP Full Stack Developer responsible for designing, developing, documenting, and supporting S/4HANA ABAP, ABAP Cloud, RAP, and Fiori applications. Support ECC-to-S/4HANA migrations, establish clean-core development standards, optimize performance, and contribute across the software development lifecycle.