Principal AI Platform Engineer

DataJobs; Cambridge (MA); On-site; USD 286,000 - 457,000; Full time

Job summary

HubSpot is seeking a Principal Machine Learning Engineer to build foundational AI infrastructure for agentive product experiences in Cambridge, MA. The role focuses on scaling systems for evaluation, quality signals, and cost efficiency across HubSpot’s AI-powered platforms.

You will lead platform engineering for agent runtime, evaluation, and model optimization, collaborating with infrastructure, product, backend, and ML teams to advance production-ready capabilities across the company.

Qualifications

• Must have deep experience with production machine learning, LLMs, or AI infrastructure.
• Experience building scalable systems where reliability, latency, quality, and cost are key constraints.
• Platform-oriented mindset focused on durable systems rather than one-off solutions.
• Ability to collaborate across infrastructure, product, backend, and ML teams.

Responsibilities

• Build infrastructure for agent runtime, evaluation, quality measurement, and model optimization.
• Create tooling to understand evaluation performance, coverage gaps, and readiness of user questions.
• Design signal pipelines to surface user frustration, agent failure states, and quality issues before CSAT drops.
• Help define a HubSpot-specific AI benchmark for evaluating model performance on HubSpot workloads.
• Build systems to evaluate new models across agents, improving product quality and reducing cost.
• Make fine-tuning and task-specific optimization more repeatable for HubSpot’s AI use cases.

Skills

Production ML

LLMs

AI infrastructure

Scalability

Reliability

Cost optimization

Cross-functional collaboration

Evaluation frameworks

Model serving

Fine-tuning

Job description

HubSpot is seeking a Principal Machine Learning Engineer to build foundational AI infrastructure for agentive product experiences in Cambridge, MA. The role focuses on scaling systems for evaluation, quality signals, and cost efficiency across HubSpot’s AI-powered platforms.

You will lead platform engineering for agent runtime, evaluation, and model optimization, collaborating with infrastructure, product, backend, and ML teams to advance production-ready capabilities across the company.