Senior Full Stack Engineer

The future of AI — whether in training or evaluation, classical ML or agentic workflows — starts with high-quality data. At HumanSignal, we’re building the platform that powers the creation, curation, and evaluation of that data. From fine-tuning foundation models to validating agent behaviors in production, our tools are used by leading AI teams to ensure models are grounded in real-world signal, not noise. Our open-source product, Label Studio , has become the de facto standard for labeling and evaluating data across modalities — from text and images to time series and agents-in-environments. With over 250,000 users and hundreds of millions of labeled samples, it’s the most widely adopted OSS solution for teams working on building AI systems. Label Studio Enterprise builds on that traction with the security, collaboration, and scalability features needed to support mission-critical AI pipelines — powering everything from model training datasets to eval test sets to continuous feedback loops.We started before foundation models were mainstream, and we’re doubling down now that AI is eating the world. If you're excited to help leading AI teams build smarter, more accurate systems — we’d love to talk. This is a product-engineering role: not “build what you’re told,” but shape what we build —own the problem, propose solutions, and ship outcomes that matter to users and the business. About the role We’re hiring a Senior Full-Stack Engineer with product vision . You’ll build end-to-end features across React/TypeScript and Python/Django , shaping APIs, data models, and background jobs while keeping UIs fast, accessible, and trustworthy. You’ll partner early with PM/Design to frame problems, prototype to learn, and make pragmatic scope calls—so complex, data-heavy workflows feel simple , performant , and reliable . Responsibilities Build full-stack features: React/TypeScript on the client; Django/REST services, data models, and background jobs on the server. Own outcomes, not tasks: refine scope, suggest trade-offs, propose simpler approaches, and land increments that deliver value fast. Design clean API contracts and evolve schemas/migrations; improve performance and reliability (query tuning, caching, job orchestration). Partner with Product Design from discovery to delivery: clarify user jobs, write lightweight RFCs/PRDs, and shape scope and milestones. Keep UIs accessible and responsive; add solid error-handling and failure-mode UX. Raise engineering standards: testing strategy, code quality, observability hooks, resilience patterns. Partner with Support to investigate production issues, reduce UX papercuts, and turn learnings into fixes. Engage with our open-source community (issues, discussions) to understand real-world needs and improve developer experience. Participate in architecture discussions and code reviews; mentor teammates and improve patterns across the codebase. What you’ll bring Senior-level experience shipping production full-stack features (React/TypeScript + Python/Django + SQL). Strong product sense : you’ve made scope/trade-off decisions and iterated based on real-world usage and feedback. Fluency with modern FE tooling (e.g., Vite/Webpack, Jest/Cypress) and state-management patterns. Backend depth: REST API design, relational modeling, migrations, performance tuning, and background job patterns. Excellent communication at a Senior IC level—you write clear RFCs/PRDs, give actionable reviews, and present trade-offs well. Nice to have: GraphQL familiarity; Kafka/queues/streaming; Spark/BigQuery; auth/RBAC; multi-tenant SaaS; design-system experience. Our stack Python/Django, JS/TS, React, OpenAI API, Spark, BigQuery, Kafka, Jest, Cypress, AWS, Kubernetes, Postgres, Redis. How we build Trunk-based development with small, reviewable PRs; feature flags for safe rollouts; strong code reviews; pragmatic testing; and close collaboration with Product/Design/Support. ... (truncated, view full listing at source)