Backend Software Engineer (Senior)

About Mercor

Mercor is training models that predict how well someone will perform on a job better than a human can. We use our platform to source, vet, and onboard expert contractors who help train AI models in a wide variety of domains. Our technology is so effective it’s used by all of the top 5 AI labs.
We scaled from $1–500M in revenue run rate in the last 17 months, making us the fastest growing company in the world. Our growth is accelerating: 11% week-over-week in July, 18% in August, and 19% in September. The team is small, profitable, and growing as fast as we can hire exceptional people.

About the Role

As a Senior Software Engineer at Mercor, you’ll take end-to-end ownership of complex projects that power the workflows of the world’s leading AI companies. You’ll architect and scale distributed systems, mentor other engineers, and set technical direction for high-impact initiatives. This role goes beyond coding: you’ll help shape engineering culture, influence product decisions, and ensure our systems scale in lockstep with our hyper-growth.

What You’ll Do

• Design, build, and scale production-grade backend APIs, services, and infrastructure.

• Take ownership of system design and architecture decisions that impact core workflows.

• Mentor and support junior engineers through code reviews, pair programming, and design discussions.

• Partner with Product and Design to deliver features quickly without sacrificing quality or scalability.

• Anticipate technical bottlenecks, propose solutions, and drive initiatives that increase reliability.

• Contribute to the systems that enable OpenAI, Anthropic, Google, and others to train and evaluate their models.

What We’re Looking For

• Strong coding fundamentals in Python (our primary backend), though interviews are language-agnostic.

• Deep understanding of distributed systems, scalability challenges, and system design.

• Experience shipping production systems at scale in high-growth or high-stakes environments.

• Ability to reason about trade-offs and make decisions balancing speed and reliability.

• Strong communication skills with an ability to align technical and business goals.

• Bias toward ownership, curiosity, and delivering simple solutions to complex problems.
  

Why Mercor

• Impact: Your work powers how the world’s leading AI labs train and test their models.

• Learning: Get early insights into frontier model capabilities months before the market.

• Growth: Work on both infrastructure and research-adjacent projects with fast paths to ownership.