UI Engineer

Job Title: Senior UI Engineer (React & Design Systems) Role Overview We are seeking an experienced, results-driven Senior UI Engineer to join our established Agile Scrum team for a 6-month strategic engagement. In this role, you will contribute directly to our shared UI framework-the component, theming, state, and API-access layer powering our next-generation enterprise user interfaces deployed across edge/on-premises and cloud targets. This is a hands-on, high-impact delivery role where you will work alongside permanent engineering staff to build, harden, and scale reusable design system components and complex feature surfaces. You will solve challenging front-end problems, including high-frequency data rendering, performance profiling, accessibility compliance, and cross-target correctness. If you possess deep expertise in modern React and TypeScript and a passion for crafting robust design systems, we want to hear from you. Key Responsibilities Framework & Component Development

• Design Systems: Build, extend, and harden reusable React and TypeScript components within our design system, covering states, theming/tokens, keyboard interaction, and strict accessibility standards.
• Feature Surfaces: Implement assigned user interfaces and complex workflows against defined UX designs and REST/streaming APIs, managing robust data fetching, caching, and offline/degraded-connectivity states.
• Cross-Target Correctness: Ensure seamless UI execution across diverse target environments (edge/on-premises and cloud-hosted deployments), supported browsers, and screen sizes.

Quality, Testing & Performance

• Test Automation: Write and maintain comprehensive unit and component tests using Jest/Vitest and React Testing Library, contributing automated end-to-end coverage for all delivered flows.
• Performance Tuning: Diagnose and resolve front-end performance bottlenecks, including bundle size reduction, render cost profiling, large data-set rendering, and memory retention in long-running sessions.
• Defect Resolution: Take assigned defects from triage to verified fix, providing thorough root-cause documentation.

Collaboration & Handover

• Agile Delivery: Participate actively in all Agile ceremonies (backlog refinement, estimation, daily standups, sprint reviews, and retrospectives) within a 3-week sprint cycle.
• Documentation: Leave behind clean component documentation, usage examples, and architectural decision notes to ensure seamless ownership by the permanent team post-engagement.

Qualifications & Requirements Minimum Qualifications

• Education: Bachelor's degree in Computer Science, Software Engineering, or a related technical field (or equivalent demonstrated professional experience).
• Experience Baseline: Minimum of 4+ years building production web front-ends.

• Technical Mastery: oDeep, current expertise in TypeScript and React (hooks, component composition, state management, and rendering behavior). oFluent modern HTML and CSS (responsive layouts, modern theming, CSS modules or CSS-in-JS). oDemonstrated experience building or extending a reusable component library or design system consumed by multiple applications. oStrong debugging and performance analysis skills using browser developer tools (profiling render cost, tracing network behavior, isolating memory growth). • Core Competencies: Clear understanding of architecture boundaries (application code vs. UI framework vs. REST API); fluent in CI/CD workflows (small PRs, automated testing, code reviews); comfortable working across Windows and Linux development environments. Preferred Attributes

• Experience implementing accessibility standards against WCAG 2.1 AA (ARIA patterns, keyboard-only navigation).
• Familiarity with back-end integration (Node.js/BFF or .NET/C#) to debug across the API boundary; Angular familiarity is a plus.
• Experience building UIs for real-time or high-frequency data streams (WebSockets/SSE, virtualized tables, time-series charting).
• Background in developing, testing, and publishing browser extensions (Chrome/Edge).
• Prior domain experience in industrial control, IoT, operational technology, or complex enterprise SaaS platforms.

Equal Opportunity Employer / Disabled / Protected Veterans The Know Your Rights poster is available here: The pay transparency policy is available here: For temporary assignments lasting 13 weeks or longer, AllSTEM Connections is pleased to offer major medical, dental, vision, 401k and any statutory sick pay where required. We are committed to working with and providing reasonable accommodations to individuals with disabilities. If you need a reasonable accommodation for any part of the employment process, please contact your staffing representative who will reach out to our HR team. AllSTEM Connections participates in the E-Verify program in certain locations as required by law. Learn more about the E-Verify program. We also consider for employment qualified applicants regardless of criminal histories, consistent with legal requirements, including, if applicable, the City of Los Angeles' Fair Chance Initiative for Hiring Ordinance. Pursuant to applicable state and municipal Fair Chance Laws and Ordinances, we will consider for employment-qualified applicants with arrest and conviction records, including, if applicable, the San Francisco Fair Chance Ordinance. For Los Angeles, CA applicants: Qualified applications with arrest or conviction records will be considered for employment in accordance with the Los Angeles County Fair Chance Ordinance for Employers and the California Fair Chance Act. Additional Skills (none specified) AllSTEM Representative Contact Info Account Executive: Nichols Branch Phone: View phone number on click.appcast.io Location: Ontario, CA AllSTEM Connections