Principal Engineer (Backend / Platform)

Blitzy • Cambridge, MA

2d • Onsite

About The Position

We are hiring a Principal Engineer to take full, hands-on ownership of Blitzy’s 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.

Requirements

• Backend: Python
• Cloud & Infrastructure: GCP (primary), Terraform
• APIs & Services: RPC-based services, microservices architectures
• Datastores: Production databases and distributed systems
• Graph databases (Neo4j) for modeling and searching complex relationships
• Vector databases / embeddings infrastructure for semantic search and retrieval
• Enterprise systems: Core understanding of how large-scale enterprise systems are designed, integrated, deployed, and operated
• Experience working within — or modernizing — complex, long-lived production environments
• AI / LLM Tooling: Experience building and operating LLM-powered systems in production
• Designing and implementing LLM validation loops (evaluation, feedback, regression testing, and failure analysis)
• LangSmith (or equivalent tooling) for tracing, evaluation, and debugging
• Supporting languages: Node.js and JavaScript
• Production systems: Monitoring, reliability, scalability, and operational tooling

Nice To Haves

• Familiarity with specific models or vendors (e.g., OpenAI, Anthropic) is a plus, but production engineering judgment and system design matter far more than any individual tool.
• Prior experience operating at Principal Engineer / Staff+ scope at a highly technical company.
• Deep understanding of how enterprise software systems are built and evolved at scale, including tradeoffs around reliability, change management, and long-term maintainability.
• Clear ownership of complex systems that you designed, built, and supported in production.
• Hands-on ownership of LLM validation loops used to ensure correctness and durability in real environments.
• Experience designing systems that combine graph, vector, and traditional data models to support reasoning over complex domains.
• Proven ability to deliver outsized impact through the right features, not just more code.

Responsibilities

• Independently own mission-critical production systems end-to-end.
• Ship high-leverage features that materially improve reliability, performance, and customer value.
• Raise the technical bar through working code and outcomes, not reviews alone.
• Identify and resolve the hardest technical bottlenecks limiting quality or velocity.
• Make technical decisions with long-term impact and stand behind them in production.
• 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 Blitzy using Blitzy, holding the platform 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.

Benefits

• Competitive salary
• Paid medical, dental, and vision insurance for you and your dependents
• 4% 401(k) match
• Equity
• Flexible vacation days, sick days, and work-from-home days
• Technology (hardware, software, reading materials, etc.) equipment and / or allowance
• The opportunity to re-shape an entire industry and create a platform that changes the future of software creation
• A beautiful office environment with adjacent offices shared by other startups — an energizing community
• Unlimited snacks, fizzy water, coffee, espresso, and whatever else you need to perform at your best

What This Job Offers

• Job Type: Full-time
• Career Level: Principal
• Education Level: No Education Listed
• Number of Employees: 1-10 employees