[Hiring] Principal Engineer @Three Pillars

Role Description

You will own meaningful, end-to-end areas of the product, spanning the agent harness, evaluation systems, platform integrations, and user interface. They are a lean team with minimal hierarchy, significant engineering autonomy, and a fast path from idea to production.

The development workflow is agent-native: coding agents are embedded throughout exploration, implementation, testing, review, and debugging, while engineers remain accountable for the quality of what reaches production. You will also work directly with customers and observe media buyers using the systems you build.

What You'll Do:

• Integrate a new advertising platform.
• Design and implement authentication, a robust API client, read and write tools with appropriate approval controls, a synchronization pipeline into Postgres, and a dedicated platform sub-agent.
• Develop model instructions that capture the platform's real-world API behavior, including nuances and constraints that may not be fully reflected in its documentation.
• Own an agent-powered product surface, including media-plan imports, campaign building and quality assurance, scheduled briefings, and Slack and email entry points.
• Eliminate a recurring class of failure by reconstructing the agent's behavior using BigQuery event logs and traces, identifying the underlying mechanism, and addressing the root cause.
• Extend the agent harness itself by improving foundational capabilities such as tool gating, context compaction, large-payload handling, and the review system.

Qualifications

• 5+ years backend engineering experience.
• Production Python experience, or equivalent depth in another language.
• Comfort with asynchronous systems, Postgres, schema design, background jobs, and the practical failure modes of distributed systems.
• Hands-on experience with LLM agent systems.
• Comfort with nondeterministic systems.
• Enough frontend experience to complete the feature, including TypeScript and React.
• A strong sense of ownership.

Requirements

• Experience in advertising technology or marketing technology, including DSPs, ad servers, attribution, or the structure of media plans.
• Deep experience with Google Cloud, particularly Vertex AI, Cloud Run, BigQuery, and Pub/Sub.
• Experience building multi-tenant SaaS products with rigorous data-isolation requirements.

Benefits

• Remote work flexibility.

Company Description

They are a small team responsible for a large product surface.