Senior Software Engineer - Customer Agent

At Klaviyo, we value the unique backgrounds, experiences and perspectives each Klaviyo (we call ourselves Klaviyos) brings to our workplace each and every day. 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. Want to learn more about life at Klaviyo? Visit klaviyo.com/careers to see how we empower creators to own their own destiny. About the Role Our team is looking for a Senior Full Stack Engineer to help build the future of Customer Agent, Klaviyo’s AI-native conversational platform. In this role, you’ll play a critical part in shaping how autonomous service, AI-driven support, and agentic commerce experiences evolve at scale across millions of customer interactions. You’ll work across the stack to design, build, and scale systems that power intelligent workflows, conversational experiences, tools integrations, retrieval systems, onboarding flows, observability, and multi-channel customer engagement. You’ll help develop both foundational platform capabilities and customer-facing experiences that enable brands to launch, customize, and continuously improve their own highly-configurable AI agents. As a Senior Engineer, you’ll tackle complex technical and product challenges, develop multiple solution paths, and evaluate business and architectural trade-offs to determine the best approach. You’ll also act as a technical leader and mentor, driving engineering quality, execution, and decision-making across projects. Additionally, you’ll be responsible for deploying well-designed, thoroughly tested solutions that prioritize reliability, scalability, and customer impact. The Customer Agent team is building one of Klaviyo’s most ambitious and strategic product areas: an extensible AI platform that enables brands to deliver personalized, autonomous customer experiences across channels like chat, email, SMS, and beyond. We operate with high ownership, rapid iteration cycles, and a strong bias toward execution. Every engineer is expected to think holistically about customer outcomes, collaborate deeply across engineering, product, design, data science, and go-to-market teams, and push beyond traditional role boundaries to help the team move faster. Success in this role means shipping high-quality systems quickly, contributing to foundational platform decisions, improving the intelligence and reliability of our agent experiences, and helping define how AI-powered customer engagement evolves at Klaviyo. What We’re Looking For A proven track record of building high-quality products and systems, with pride in writing clean, maintainable, high-quality code. 7+ years of experience in a software engineering role. Strong experience developing end-to-end software solutions or extensive experience across both front-end and back-end technologies. Experience building scalable, customer-facing systems in fast-moving product environments - we operate like a startup inside of Klaviyo. Experience leading projects and being accountable for technical and business outcomes. Experience mentoring team members or driving initiatives that help the team grow and learn new skills. Experience conducting code reviews and maintaining a robust testing and deployment cycle. Curiosity and enthusiasm for AI-native product development, including practical experience experimenting with LLMs, AI tooling, or agentic workflows in professional or personal projects. Excitement about leveraging AI to improve engineering velocity, customer experiences, and operational workflows. A strong product mindset and willingness to collaborate cross-functionally to solve ambiguous problems with urgency and pragmatism. Nice to Have Skills with Python and related technologies. Skills with React and related technologies. Experience building conversational AI systems, workflow engines, or agentic platforms. Experience with retrieval systems, embeddings, eval frameworks, or LLM orchestration patterns. Experience building cloud-native solutions, ideally with AWS. Experience developing customer support, commerce, marketing, or customer data software solutions. Experience with machine learning systems or AI infrastructure. Experience building multi-tenant or highly configurable SaaS platforms. Familiarity with observability, tracing, experimentation, or AI quality/evaluation tooling. We use Covey as part of our hiring and / or promotional process. For jobs or candidates in NYC, certain features may qualify it as an AEDT. As part of the evaluation process we provide Covey with job requirements and candidate submitted applications. We began using Covey Scout for Inbound on April 3, 2025. Please see the independent bias audit report covering our use of Covey here . #indeedRD Massachusetts Applicants: It is unlawful in Massachusetts to require or administer a lie detector test as a condition of employment or continued employment. An employer who violates this law shall be subject to criminal penalties and civil liability. Our salary range reflects the cost of labor across various U.S. geographic markets. The range displayed below reflects the minimum and maximum target salaries for the position across all our US locations. The base salary offered for this position is determined by several factors, including the applicant’s job-related skills, relevant experience, education or training, and work location. In addition to base salary, our total compensation package may include participation in the company’s annual cash bonus plan, variable compensation (OTE) for sales and customer success roles, equity, sign-on payments, and a comprehensive range of health, welfare, and wellbeing benefits based on eligibility. Your recruiter can provide more details about the specific salary/OTE range for your preferred location during the hiring process. Base Pay Range For US Locations: $148,000 — $222,000 USD This role may require up to 10% travel for purposes such as new hire onboarding, client or partner work if applicable, team meetings, and industry events. Travel is coordinated in advance. Get to Know Klaviyo We’re Klaviyo (pronounced clay-vee-oh). We empower creators to own their destiny by making first-party data accessible and actionable like never before. We see limitless potential for the technology we’re developing to nurture personalized experiences in ecommerce and beyond. To reach our goals, we need our own crew of remarkable creators—ambitious and collaborative teammates who stay focused on our north star: delighting our customers. If you’re ready to do the best work of your career, where you’ll be welcomed as your whole self from day one and supported with generous benefits, we hope you’ll join us. AI fluency at Klaviyo includes responsible use of AI (including privacy, security, bias awareness, and human-in-the-loop). We provide accommodations as needed. By participating in Klaviyo’s interview process, you acknowledge that you have read, understood, and will adhere to our Guidelines for using AI in the Klaviyo interview Process . For more information about how we process your personal data, see our Job Applicant Privacy Notice . Klaviyo is committed to a policy of equal opportunity and non-discrimination. We do not discriminate on the basis of race, ethnicity, citizenship, national origin, color, religion or religious creed, age, sex (including pregnancy), gender identity, sexual orientation, physical or mental disability, veteran or active military status, marital status, criminal record, genetics, retaliation, sexual harassment or any other characteristic protected by applicable law. IMPORTANT NOTICE: Our company takes the security and privacy of job applicants very seriously. We will never ask for payment, bank details, or personal financial information as part of the application process. All our legitimate job postings c