Principal Engineer (Backend / Platform)

Blitzy is a Cambridge, MA based rapidly scaling Generative AI start-up. The Blitzy platform enables thousands of AI Agents to ‘think’ and cooperate for hours to generate high-quality code at scale for enterprises. The platform specializes in working with large-scale enterprise codebases and executing large-scale changes. The platform builds everything AI can deliver in a precise manner — around 80% of any roadmap or large-scale feature addition — supplemented with 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, Blitzy is actively hiring senior technologists in Cambridge, MA who have a passion for building AI that leverages “System 2 Thinking” to solve problems at inference. The company is rapidly growing. Compensation: Expected total compensation is in the range of $300K–$500K , with a mix of cash and equity that reflects the scope, ownership, and impact of the role. Final packages are tailored to demonstrated Principal-level experience and production ownership. Location: One Kendall Square, Cambridge MA 02139 (In-person role) The Role 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. What Success Looks Like 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 Areas of Ownership 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 Core Technologies & Required Experience 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) Expertise across at least two of AWS, GCP, and Azure, with GCP mandatory Expert‑level Kubernetes experience for container orchestration in production environments Terraform for infrastructure as code Production systems: monitoring, reliability, scalability, and operational tooling Databases & Data Systems Strong expertise across both SQL and NoSQL databases SQL: PostgreSQL, MySQL, or similar relational databases Graph databases (Neo4j) for modeling and searching complex relationships Vector databases / embeddings infrastructure for semantic search and retrieval 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 Familiarity with specific models or vendors (e.g., OpenAI, Anthropic) is a plus Frontend & Full‑Stack Competency Strong understanding of frontend frameworks and architecture Ability to evaluate and contribute to frontend technical decisions Demonstrated technical expertise across the full stack — you can debug, design, and ship across frontend, backend, infrastructure, and AI layers Core understanding of how large‑scale enterprise systems are designed, integrated, deployed, and operated Experience working within — or modernizing — complex, long‑lived production environments Ways to Stand Out 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 Track record of being a self‑learner who requires minimal supervision and gets things done without compromising on quality Compensation Total compensation: $300,000 - $500,000 This includes a mix of competitive base salary and equity, tailored to demonstrated Principal-level experience, scope of ownership, and production impact. You’ll Get… Competitive salary and equity Paid medical, dental, and vision insurance for you and your dependents 4% 401(k) match 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 Culture We work hard, maintain a curious mindset, and believe deeply in a low‑ego, high‑output approach. The IC (individual contributor) is the most critical, respected role in the company. We manage the work, not the people. Blitzy is roughly 60 employees today, and will be doubling in headcount over the next 6‑8 months. This is a high growth company operating at a high growth pace. We move fast on all two‑way door decisions. A good decision made today is better than a “perfect” decision made a week from now. We believe in being an everyday athlete so you can bring your best mind to work. We promote great sleep, daily motion and movement, and whatever restorative activities help you reach optimal mental performance. This leads to a happier, healthier, and more productive team. What We Ask of You Please ask yourself whether you are ready for a challenge before applying. Even in optimal conditions, startups are hard. The work is intense, priorities shift, and what you're working on week‑to‑week will change. If that feels exciting rather than concerning, that's a good sign. Startups also require a high degree of autonomy. We are in person, and we bring relevant experience — but we do not have all the answers. Like every startup, we continue to discover as we build. If that excites you, we'd love to hear from you. To Apply Apply through this posting. Process Here’s what you can expect: 4 interviews Notification of offer with timeline to accept #J-18808-Ljbffr Blitzy AI