Senior Full Stack Engineer

Job Description

Job Description

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

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.

How we work

At HumanSignal, we follow a six-week cycle known as "Build and Ship" followed by a "Cooldown." During the first four weeks, the team focuses on creating new features and shipping improvements. We also rotate a small group to handle customer support, ensuring everyone stays in touch with real user needs and we can respond quickly to issues.

After those four weeks, we have a two-week "Cooldown" period. This is when we tackle technical debt, refine our integration processes, and wrap up those lingering tasks that never quite fit into regular sprints but really help us feel good about our codebase and workflows.

Location & Compensation

At HumanSignal we pay based on regional compensation market rate ranges across the globe. We are hiring for this role across North and South America as well as Europe. The base cash compensation range is $140,000 to $200,000 USD. These ranges are provided by market data and are in good faith. The final offer details are determined by several factors including candidate experience, expertise, as well as applicable industry knowledge and may vary from the pay ranges listed above.

It's an exciting time at HumanSignal. We're growing quickly, and roles evolve as we learn. We've put thought into your first initiatives, but we'll refine them together. If this sounds exciting, come build with us.