Lead Engineer

Who you are

• You've built, scaled, and supported production agentic systems, not just prototyped them: real orchestration, evals, guardrails, and non-deterministic failure handling. You've owned your part of one through launch, incidents, and the operational reality after the demo
• You've learned the hard lessons that only come from running agents in production: securing them against misuse and abuse, and the operational scar tissue of keeping a non-deterministic system reliable as usage grows
• You've owned technical and product direction for a significant area before, not just your own component, and you can point to something you designed and championed that shipped and that other engineers built on
• You're hands-on: writing code, reviewing your own and others’ architecture decisions, and debugging production issues yourself, not delegating the hardest problems away
• Your patterns and designs are reused by other engineers, and you've unblocked many others’ projects, not just your own
• You communicate complex technical trade-offs clearly across engineering and product audiences, and you can turn an undefined problem into a plan others rally behind
• Experience working on a multi-tenant agent platform at production scale, where external customers configure their own agent behavior on shared infrastructure
• Experience building 0-to-1 products or working in startup environments
• A track record with production evaluation systems, AI observability, or human-in-the-loop workflows for LLM-powered products
• We believe everyone deserves a fair shot at success and appreciate the experiences each person brings beyond the traditional job requirements. If you’re a close but not exact match with the description, we hope you’ll still consider applying

What the job involves

• Our Engineering team builds the AI systems that power how brands run their businesses on Klaviyo. We move fast, ship in production, and hold a high bar for what "AI-native" actually means: systems that make real judgment calls, not demos
• The Customer Agent team is one of the newest and most ambitious groups in that org, based in Boston and working in-office: we're building a conversational AI system that lets brands serve their own customers at a scale no human support team could match
• We're still small enough that one engineer’s work visibly shapes how the whole platform evolves. We're past the demo stage: the team ships changes against live customer traffic, measures quality with real evaluation frameworks, and treats reliability as a product feature, not an afterthought
• As Lead Engineer, you'll set the technical and product direction for a core area of Customer Agent end to end, building a 0-to-1 agentic product with the speed and ownership of a startup, backed by the scale and resources of one of the most innovative tech companies on the East Coast, while staying hands-on with the hardest problems yourself
• This is a lead role, with a wide footprint across our agentic product - from orchestration to governance - that grows based on where the product is when you join
• We're looking for an engineer who owns complex, ambiguous problems, who has built, scaled, and supported a production agentic system through everything that comes after the demo, and who up-levels the people, process, and technology around them
• Set the technical and product direction for a core area of Customer Agent, from architecture through production, and contribute to the direction of the platform overall
• Take on the hardest technical problems in your area: orchestration, evaluation, guardrails, memory & context, failure handling for non-deterministic systems
• Write and ship code, review designs, and make the hard calls in your area when there’s no obvious right answer
• Define patterns that other engineers adopt, and mentor through design reviews rather than direct management
• Partner with product, design, data science, and go-to-market leaders to shape what gets built, not just how it’s built
• Evaluate emerging AI technologies and bring the ones worth betting on into production

Benefits

• Private medical insurance
• Medical
• Dental
• Vision
• Lifestyle spending account
• Commuter benefits
• Modern Health - wellness platform
• Parental leave
• Company equity
• Employee stock purchase plan
• Health savings account (HSA)
• Flexible spending accounts (FSAs)
• Employee assistance program (EAP)
• 401(k) plan with company match
• Flexible paid time off (FPTO)
• 13 company holidays
• Paid parental bonding leave
• Medical, Dental, Vision
• Pension
• Financial coaching
• Life insurance
• Income protection
• Annual leave - up to 25 annual leave days
• 10 company holidays (8 bank holidays + 2 recharge days)
• Family leave
• Cycle to Work benefit
• Mental health benefits