Senior Software Engineer, Agent Platform

<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>&nbsp;to see how we empower creators to own their own destiny.</em></p></div><h2>Senior Software Engineer - Agent Platform</h2> <p>At Klaviyo, we believe the future of software lies not in productivity tools for human users but in software that can run and optimize itself based on outcome or reward metrics. We’ve built the infrastructure and application that serve as the interface between businesses and consumers. We now have over 167,000 customers, billions of consumer profiles, and hundreds of billions of customer messages and follow-on conversion data. We have a big opportunity to build state-of-the-art AI and machine learning technologies at Klaviyo to power our products and develop AI agents that can automatically create and execute marketing or customer experiences, strategies, and campaigns for any business.</p> <p>As a <strong>Senior Software Engineer, Agent Platform</strong>, you’ll play a key role in designing and scaling the backend systems that power our AI products and agent solutions. This backend-heavy role gives you opportunities to influence architecture, async processing, and distributed systems. You’ll collaborate closely with product managers, ML engineers, and data scientists to deliver real-world impact at scale.</p> <p><em>This role is hybrid and based in Boston.</em></p> <p><strong>How you'll make a difference:</strong></p> <ul> <li>Design and build backend systems to scale AI solutions for 167K+ customers.</li> <li>Contribute to our agentic architecture to support performant AI agents.</li> <li>Build tools to tune LLM-based features, deploy agents, MCP and RAG in production, and evaluate performance using tools like Arize, OpenAI, Bedrock, LangChain, vLLM and Ray.</li> <li>Develop reliable, scalable data pipelines and APIs for AI systems.</li> <li>Foster a culture of ownership, experimentation