Senior Software Engineer, Annotations

About Handshake AI

Human data is the core infrastructure to AI advancement. Frontier AI labs currently improve model capabilities with various data-intensive post-training techniques. We believe that data spend for AI training will increase by 3-5x in the next few years and continue for much longer as models take on new domains. Handshake AI supports all of the frontier AI labs, working on their most complex data at the largest scale.

The Role

We’re looking for a Senior Software Engineer to join our Annotations team and build the systems that power high-quality human data for frontier AI companies. You’ll work at the intersection of product engineering, distributed systems, and AI data operations—designing tools that help operators manage annotation projects, improve task quality, and scale expert workflows.

This is a high-ownership role in a fast-moving environment. You’ll partner closely with product, design, data, operations, and engineering teams to turn ambiguous problems into reliable, intuitive software used across the annotation lifecycle.

What you’ll do

• Build and scale operator tooling that enables teams to create, manage, prioritize, and audit annotation projects.

• Design workflows and quality-control systems that improve task accuracy, throughput, and customer outcomes.

• Develop performant full-stack features using Python, Node.js/TypeScript, React, PostgreSQL, and backend APIs.

• Establish technical direction for complex projects, balancing speed, maintainability, reliability, and operational needs.

• Partner with product, design, operations, and data teams to define requirements and ship impactful solutions.

• Lead projects from initial concept through high-quality production delivery, including rollout, monitoring, and iteration.

• Mentor engineers, raise the quality of code reviews and architecture discussions, and help unblock the team.

• Improve engineering processes, testing practices, observability, and operational health across the squad.

You have

• 6+ years of software engineering experience building and operating production systems.

• Strong proficiency in Python, Node.js, Typescript, React, PostgreSQL, and backend APIs.

• Experience designing scalable, reliable software and making sound architectural tradeoffs.

• A track record of owning complex projects from ambiguity through delivery.

• Strong product judgment and an ability to connect technical decisions to customer and business outcomes.

• Excellent communication skills and the ability to work effectively with technical and non-technical partners.

• A quality mindset: you write maintainable code, test thoughtfully, debug deeply, and address root causes.

• A collaborative leadership style, including experience mentoring engineers and elevating team practices.

• Comfort working in a high-velocity environment where priorities and requirements evolve quickly.

Bonus points

• Experience building workflow, marketplace, operations, or internal-platform software.

• Familiarity with AI/ML data pipelines, annotation systems, evaluation workflows, or human-in-the-loop products.

• Experience working with distributed teams, expert networks, or high-volume operational processes.

• Contributions to open source or a strong record of self-directed technical projects.

We offer

Handshake delivers benefits that help you feel supported and thrive at work and in life. Benefits for full-time US employees include:

• Equity in a fast-growing company

• 401(k) match, competitive compensation, and financial coaching

• Medical, dental, and vision coverage

• Mental health support and a $500 wellness stipend

• Paid parental leave, fertility benefits, and parental coaching

• $2,000 annual learning stipend

• Flexible PTO, 15 holidays, and 2 flex days

• Internet, commuting support, and free lunch and gym access in our San Francisco office

• Team outings and referral bonuses

Why join Handshake now:

• Shape how every career evolves in the AI economy, at global scale, with impact your friends, family and peers can see and feel