<div class="content-intro"><p><em>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 <a class="_ymio1r31 _ypr0glyw _zcxs1o36 _mizu194a _1ah3dkaa _ra3xnqa1 _128mdkaa _1cvmnqa1 _4davt94y _4bfu18uv _1hms8stv _ajmmnqa1 _vchhusvi _kqswh2mm _ect4ttxp _syaz13af _1a3b18uv _4fpr8stv _5goinqa1 _f8pj13af _9oik18uv _1bnxglyw _jf4cnqa1 _30l313af _1nrm18uv _c2waglyw _1iohnqa1 _9h8h12zz _10531ra0 _1ien1ra0 _n0fx1ra0 _1vhv17z1" href="http://klaviyo.com/careers" data-renderer-mark="true">klaviyo.com/careers</a> to see how we empower creators to own their own destiny.</em></p></div><p><strong>Job Title:</strong> Sr. Lead Software Engineer<br><strong>Location:</strong> Boston, MA</p> <p>This role is based in our Boston hub. We operate a hub‑first model, with regular in‑office collaboration expected.</p> <h2><strong>About the Role</strong></h2> <p>At Klaviyo, we believe the future of software isn’t just better productivity tools for humans—it’s intelligent systems that can run, optimize, and adapt themselves based on real-time outcome and reward signals. Having already built the infrastructure and applications that connect businesses with over 200,000 customers, billions of consumer profiles, and hundreds of billions of interaction events, we are now making foundational investments in Marketing AI and Service AI to power next-generation agentic capabilities across our entire ecosystem.</p> <p>The Klaviyo Orchestrate pillar drives the core platform experience, providing the high-throughput capabilities our customers use daily to manage and execute complex marketing workflows. This team balances strict Tier-1 availability and low-latency scalability requirements with rapid agility across the Klaviyo ecosystem. Internally, we have fully embraced AI-native engineering methodologies and are dedicated to putting sophisticated AI-native capabilities directly into the hands of our builder-customers.</p> <p>We are building a best-in-class, flexible orchestration platform designed to handle massive scale while continuously advancing reliability and performance to meet the expanding needs of our global customer base.</p> <h2><strong>How You’ll Make a Difference</strong></h2> <ul> <li>Architect and scale Klaviyo’s Core Orchestration platform, supporting high-traffic, low-latency services with extreme reliability.</li> <li>Drive the technical vision for integrating AI-driven agentic workflows and automated decision-making into core customer interactions.</li> <li>Lead the adoption of AI-native software development practices, continually improving engineering productivity and delivery speed across the team.</li> <li>Design foundational frameworks and services adopted across engineering teams, championing high technical standards through design reviews and mentorship.</li> <li>Partner closely with product management, data science, design, and executive leaders to shape strategic roadmaps and long-term platform architecture.</li> </ul> <h2><strong>Who You Are</strong></h2> <ul> <li><strong>Experienced Backend Leader: </strong>8+ years of professional software engineering experience centered on distributed systems, microservices architecture, and high-availability backend platform ownership.</li> <li><strong>AI & Agentic Systems Practitioner: </strong>Hands-on experience shipping production LLM workflows, retrieval-augmented generation (RAG) pipelines, or agentic frameworks with a solid understanding of evals, prompt architecture, and fine-tuning.</li> <li><strong>Distributed Systems Specialist: </strong>Proven track record of architecting event-driven architectures, asynchronous processing pipelines, and message queues (e.g., Kafka, Celery, SQS, Redis) for heavy throughput workloads.</li> <li><strong>Python & Tooling Mastery: </strong>Deep proficiency in Python and modern frameworks (FastAPI, Django) alongside experience with data processing platforms and object-relational mapping tools.</li> <li><strong>Cloud Infrastructure Native: </strong>Strong expertise with AWS, Kubernetes, CI/CD automation, and modern observability suites, integrating cloud architecture seamlessly into system design.</li> <li><strong>Quality & Evals Focused: </strong>Experience establishing automated evaluation frameworks for AI models, balancing latency, accuracy, cost, and safety in production environments.</li> <li><strong>Cross-Functional Influencer: </strong>A technical leader who elevates team performance through architectural direction, collaborative problem-solving, and clear communication across engineering and business domains.</li> <li><strong>Collaborative and customer‑first.</strong> You’re comfortable collaborating directly with PMs, ML engineers, and customers; you can translate between customer needs, product goals, and technical constraints, and you care deeply about the customer experience.</li> <li><strong>AI-First Engineer: </strong>Active use of AI coding tools and modern agentic development workflows in daily work to accelerate innovation and shorten feedback cycles.</li> <li><strong>Customer-Centric Mindset: <