Principal Engineer (Backend / Platform) at Blitzy – Cambridge, Massachusetts

About Blitzy

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: This role is compensated at the top of the market for Principal Engineers.

Expected total compensation is in the range of $300K–$375K plus meaningful equity value and benefits.

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 LikeYou independently own mission-critical production systems end-to-endYou ship high-leverage features that materially improve reliability, performance, and customer valueYou raise the technical bar through working code and outcomes, not reviews aloneYou identify and resolve the hardest technical bottlenecks limiting quality or velocityYou make technical decisions with long-term impact and stand behind them in productionYou are a self-directed learner requiring minimal supervisionYou are dedicated to getting things done right without making technical compromisesYou demonstrate strong technical expertise across the full stack: frontend, backend, infrastructure, and AI systemsYou materially increase the effectiveness of the engineering organization through example and judgmentAreas of OwnershipEnd-to-end ownership of production-grade backend systems used by enterprise customersCorrectness, scalability, performance, and operational reliability in real environmentsDelivery and stewardship of high-impact features, not just incremental improvementsBuilding and improving Blitzy using Blitzy, holding the platform to real-world standardsDesigning, operating, and evolving LLM validation loops to ensure correctness, consistency, and durability in productionSetting engineering quality and durability expectations across teams without direct reportsCore 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:

BackendPython (primary language)Backend frameworks and microservices architecturesRPC-based services (REST, gRPC)Node.js and JavaScript (supporting languages)Cloud & InfrastructureExpertise across at least two of AWS, GCP, and Azure, with GCP mandatoryExpert-level Kubernetes experience for container orchestration in production environmentsTerraform for infrastructure as codeProduction systems: monitoring, reliability, scalability, and operational toolingDatabases & Data SystemsStrong expertise across both SQL and NoSQL databasesSQL: PostgreSQL, MySQL, or similar relational databasesNoSQL: MongoDB, Cassandra, DynamoDB, or similarGraph databases (Neo4j) for modeling and searching complex relationshipsVector databases / embeddings infrastructure for semantic search and retrievalAI / LLM ToolingExperience building and operating LLM-powered systems in productionDesigning and implementing LLM validation loops (evaluation, feedback, regression testing, and failure analysis)LangSmith (or equivalent tooling) for tracing, evaluation, and debuggingFamiliarity with specific models or vendors (e.g., OpenAI, Anthropic) is a plusFrontend & Full-Stack CompetencyStrong understanding of frontend frameworks and architectureAbility to evaluate and contribute to frontend technical decisionsDemonstrated technical expertise across the full stack — you can debug, design, and ship across frontend, backend, infrastructure, and AI layersEnterprise SystemsCore understanding of how large-scale enterprise systems are designed, integrated, deployed, and operatedExperience working within — or modernizing — complex, long-lived production environmentsWays to Stand OutPrior experience operating at Principal Engineer / Staff+ scope at a highly technical companyDeep understanding of how enterprise software systems are built and evolved at scale, including tradeoffs around reliability, change management, and long-term maintainabilityClear ownership of complex systems that you designed, built, and supported in productionHands-on ownership of LLM validation loops used to ensure correctness and durability in real environmentsExperience designing systems that combine graph, vector, and traditional data models to support reasoning over complex domainsProven ability to deliver outsized impact through the right features, not just more codeTrack record of being a self-learner who requires minimal supervision and gets things done without compromising on qualityCompensation

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 equityPaid medical, dental, and vision insurance for you and your dependents4% 401(k) matchFlexible vacation days, sick days, and work-from-home daysTechnology (hardware, software, reading materials, etc.) equipment and/or allowanceThe opportunity to re-shape an entire industry and create a platform that changes the future of software creationA beautiful office environment with adjacent offices shared by other startups — an energizing communityUnlimited snacks, fizzy water, coffee, espresso, and whatever else you need to perform at your bestCulture

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:

10-minute intro call4 interviewsNotification of offer with timeline to accept