Principal Engineer Jobs in Boston, MA (NOW HIRING)

We are a Cambridge, MA–based rapidly scaling Generative AI startup.

Our platform enables thousands of AI Agents to “think” and cooperate for hours to generate high-quality code at scale for enterprises. We specialize in working with large-scale enterprise codebases and executing large-scale changes. The platform delivers everything AI can produce in a precise manner — roughly 80% of any roadmap or large-scale feature addition — supplemented by a human engineering guide to complete the remaining 20% needed for production.

We deliver 3x–5x engineering velocity improvements to our enterprise customers. With over 27 patents and counting, we are actively hiring senior technologists in Cambridge, MA who are passionate about building AI that leverages “System 2 Thinking” to solve problems at inference.

We are rapidly growing.

One Kendall Square, Cambridge MA 02139 (In-person role)

We are hiring a Principal Engineer to take full, hands-on ownership of our most critical production-grade systems and to deliver high-leverage features that materially improve customer outcomes and engineering velocity.

This is the most senior individual contributor role at the company today.

This is not a Senior-plus role, an architecture-only role, or a promotion-track role. We are looking for someone who has already operated at Principal / Staff+ scope in a highly technical environment and expects to spend their time writing, reviewing, and shipping production code.

This role is 100% hands-on. Leverage comes from system ownership, execution quality, and durable technical decisions — not people management or process.

• You independently own mission-critical production systems end-to-end

• You ship high-leverage features that materially improve reliability, performance, and customer value

• You raise the technical bar through working code and outcomes, not reviews alone

• You identify and resolve the hardest technical bottlenecks limiting quality or velocity

• You make technical decisions with long-term impact and stand behind them in production

• You are a self-directed learner requiring minimal supervision

• You are dedicated to getting things done right without making technical compromises

• You demonstrate strong technical expertise across the full stack: frontend, backend, infrastructure, and AI systems

• You materially increase the effectiveness of the engineering organization through example and judgment

• End-to-end ownership of production-grade backend systems used by enterprise customers

• Correctness, scalability, performance, and operational reliability in real environments

• Delivery and stewardship of high-impact features, not just incremental improvements

• Building and improving the platform using the platform itself, holding it to real-world standards

• Designing, operating, and evolving LLM validation loops to ensure correctness, consistency, and durability in production

• Setting engineering quality and durability expectations across teams without direct reports

This role demands strong, hands-on experience across the full technology stack. You should have deep expertise in most of the following:

• Python (primary language)

• Backend frameworks and microservices architectures

• RPC-based services (REST, gRPC)

• Node.js and JavaScript (supporting languages)

• Expertise across at least two of AWS, GCP, and Azure (GCP mandatory)

• Expert-level Kubernetes experience in production environments

• Terraform for infrastructure as code

• Production systems: monitoring, reliability, scalability, and operational tooling

• Strong expertise across both SQL and NoSQL databases

• SQL: PostgreSQL, MySQL, or similar

• NoSQL: MongoDB, Cassandra, DynamoDB, or similar

• Graph databases (Neo4j) for modeling complex relationships

• Vector databases and embeddings infrastructure for semantic search

• Experience building and operating LLM-powered systems in production

• Designing and implementing LLM validation loops (evaluation, feedback, regression testing, failure analysis)

• LangSmith or equivalent tooling for tracing and evaluation

• Familiarity with models or vendors such as OpenAI or Anthropic is a plus

• Strong understanding of frontend frameworks and architecture

• Ability to evaluate and contribute to frontend technical decisions

• Proven ability to debug, design, and ship across frontend, backend, infrastructure, and AI layers

• Deep understanding of large-scale enterprise system design and operation

• Experience modernizing or working within long-lived production environments

• Prior experience operating at Principal Engineer / Staff+ scope

• Clear ownership of complex systems built and supported in production

• Hands-on ownership of LLM validation loops in real environments

• Experience combining graph, vector, and relational data models

• Proven ability to deliver outsized impact through the right features

• Track record of self-direction and uncompromising quality

• Competitive salary and equity

• Medical, dental, and vision insurance for you and your dependents

• 4% 401(k) match

• Flexible vacation, sick days, and work-from-home days

• Technology and learning allowance

• The opportunity to reshape an entire industry

• A beautiful office environment in a vibrant startup community

• Unlimited snacks, coffee, espresso, and everything you need to perform at your best

We work hard, stay curious, and believe in a low-ego, high-output approach. The individual contributor is the most respected role in the company. We manage the work, not the people.

We are roughly 60 employees today and expect to double headcount over the next 6–8 months. This is a high-growth company operating at high speed.

We move fast on two-way door decisions. A good decision today beats a perfect decision next week.

We believe in being everyday athletes — prioritizing sleep, movement, and restorative habits to bring our best minds to work.