Senior Lead AI Engineer - Agentic Systems & LLMs

At Klaviyo, we empower global brands and e-commerce creators to make first-party data actionable. Our Applied AI group builds production-grade, AI-native systems that handle real business judgment calls for tens of thousands of customer-facing brands.

As a Senior Lead Engineer on the Customer Agent team, you will set the technical and product direction for a 0-to-1 conversational AI agent platform that enables brands to deliver autonomous customer support at massive scale. This is a principal-caliber individual contributor role for a hands-on engineer who has personally architected, deployed, and scaled production agentic systems past the demo stage. Operating in an in-office environment in Boston, you will solve the platform’s hardest non-deterministic engineering challenges—including agent orchestration, real-time evaluation frameworks, safety guardrails, context management, and self-healing mechanisms—while remaining actively hands-on in the codebase.

Key Responsibilities

• Technical & Product Architecture: Set end-to-end technical direction for the Customer Agent platform, converting ambiguous problem spaces into production-ready architectural blueprints.
• Hands-On Core Engineering: Solve complex non-deterministic system problems personally—writing clean code, conducting architectural design reviews, and debugging production incidents.
• Agentic Infrastructure: Architect robust orchestration engines, context memory stores, LLM guardrails, failure-handling mechanisms, and automated evaluation frameworks.
• Cross-Functional Alignment: Partner directly with Product Management, Design, Data Science, and Go-to-Market leaders to shape the strategic roadmap and product vision.
• Force Multiplier & Mentorship: Build reusable frameworks and platform abstractions that other engineering teams adopt; mentor senior engineers through technical guidance and design reviews rather than direct line management.
• Emerging AI Technology Evaluation: Continuously evaluate frontier LLM models, agentic frameworks, and AI tools, integrating high-value advancements directly into production.

Requirements

Deep Agentic & AI Systems Expertise

• Demonstrated track record as a Principal or Senior Lead Engineer having architected, built, scaled, and operated a production agentic system end-to-end through launch, scale, and operational incidents.
• Deep, hands-on experience solving operational challenges unique to running agents in production: non-deterministic failure handling, prompt injection defense, agent abuse mitigation, and context window optimization.
• Proven experience setting product-level technical strategy and building shared frameworks/architectures that were adopted across multiple engineering teams.
• Hands-On Coding & Execution: Active involvement in writing production code, reviewing architecture decisions, and debugging live production issues without delegating core technical challenges.
• Outstanding technical communication skills—ability to convey complex AI trade-offs clearly to executive, product, and engineering audiences.

Work Logistics

• Ability to work in-office at Klaviyo’s headquarters in Boston, MA.

Preferred Qualifications

• Experience operating a multi-tenant agent platform at production scale, where external clients configure custom agent behavior on shared infrastructure.
• Track record in 0-to-1 product development or high-growth startup engineering environments.
• Practical experience with production evaluation systems (evals), AI observability pipelines, and human-in-the-loop (HITL) workflows for LLM-powered products.

Total Rewards & Benefits

• Compensation & Equity: Base salary of $216,000 – $324,000 USD + participation in annual cash bonus plan + competitive equity grants.
• Comprehensive Healthcare: Robust medical, dental, and vision insurance options for employees and eligible dependents.
• Financial Security & Retirement: 401(k) retirement savings plan, life insurance, and disability coverage.
• Workplace Culture & Perks: Onsite collaboration at Boston HQ, professional development stipends, and dedicated AI productivity tool access.