Senior Backend Engineer

Real-world data is the competitive edge in AI.

HumanSignal is a human data partner for companies building AI models and products. Our customers ship better AI, faster, because we partner with their researchers from real-world data creation to annotation to delivery.

We design and create datasets from scratch, recruit and manage the domain experts who evaluate model output, and run everything through our own platform, Label Studio, the open-source standard for data labeling and evaluation, used by over 1 million practitioners worldwide.

We specialize in the operationally complex: real-world data collection, multimodal pipelines, and multi-step workflows. Advanced ML and AI teams use our enterprise platform to run their own data factories, and our services team to extend their reach where in-house capacity runs out.

If you want to do work that materially shapes how the next generation of AI products gets built, 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.

We’re hiring a Senior Backend Engineer with product vision. You’ll design and operate services in Python/Django that power labeling and evaluation workflows at scale: clean API contracts, robust data models, efficient background jobs, and dependable performance. You’ll partner early with PM/Design/FE to frame problems, prototype to learn, and make pragmatic scope calls—so complex workflows feel simple, reliable, and fast for users.

• →Design, build, and operate backend services/APIs in Python/Django with Postgres/Redis.
• →Own outcomes, not tasks: refine scope, suggest trade-offs, and land increments that deliver value quickly and safely.
• →Model data and author migrations; tune queries and caching; manage background jobs/queues for high-volume workflows.
• →Evolve API contracts with FE; keep interfaces clear, versioned, and resilient to change.
• →Improve reliability and performance (timeouts, retries, idempotency, rate limits, pagination, backpressure).
• →Implement secure, multi-tenant patterns: auth, permissions/RBAC, auditability, and safe data boundaries.
• →Contribute to testing strategy (unit/integration), error handling, and graceful failure modes.
• →Partner with Support to investigate production issues and turn learnings into fixes and prevention.
• →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.
  
  

• Senior-level experience shipping production backends in Python/Django (or a close equivalent) and SQL.
• Strong product sense: you’ve made scope/trade-off decisions and iterated based on real-world usage and feedback.
• Depth in REST API design, relational modeling, migrations, and performance tuning.
• Experience with background processing/queues (e.g., Celery/RQ/Kafka-backed workers) and operational concerns.
• Clear written communication at a Senior IC level—concise RFCs/PRDs, actionable reviews, and crisp decision records.
• Nice to have: GraphQL familiarity; Kafka/streaming; Spark/BigQuery; security/compliance exposure; multi-region architectures.
  
  

Python/Django, JS/TS, React, OpenAI API, Spark, BigQuery, Kafka, Jest, Cypress, AWS, Kubernetes, Postgres, Redis.

Trunk-based development with small, reviewable PRs; feature flags for safe rollouts; strong code reviews; pragmatic testing; and close collaboration with Product/Design/Support.

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.