Senior Software Engineer - Marketing Agent

About the Role

At Klaviyo, we believe the future of software lies not in productivity tools for human users but in systems that do the hard work for them. We’ve built the infrastructure and applications that power the interface between businesses and consumers — supporting over 183,000+ customers, billions of consumer profiles, and hundreds of billions of customer interactions. Now, we’re building the next generation of AI agents that can automatically create, execute, and optimize marketing and customer experience strategies for any business.

As a Senior Software Engineer on Klaviyo's Marketing Agent team, you'll be at the forefront of one of the most impactful bets we're making — building an AI-powered system that autonomously creates and executes high-stakes marketing strategies on behalf of thousands of customers. This isn't backend plumbing: the work you ship directly drives revenue for the businesses that rely on Klaviyo every day. Partnering closely with product managers and technical product owners, you'll shape the scope of what's possible, turn ambitious ideas into production reality, and craft tools so intuitive they feel like superpowers to the marketers using them.

This role is primarily backend, with a strong focus on crafting robust and maintainable AI powered systems that deliver high quality strategies and marketing content that’s ready to use to our customers. There are ample opportunities for growth given the scope of this role and the team’s central role in Klaviyo’s product.

How you’ll make a difference

• You will dramatically increase ROI for Klaviyo customers by automating most of the marketing process for them.
• You will lead and design the next generation of agentic systems at Klaviyo, pushing the frontier of AI capabilities.
• You will collaborate with AI Engineers and AI Infra Engineers to ensure our system consistently produces high quality outputs at low latency.
• You will leverage your experience to mentor and level up junior team members on engineering best practices and patterns.
• You will transform workflows by putting AI at the center, building smarter systems and ways of working from the ground up.

Who you are

• A proven track record of building high-quality products and systems, with pride in writing clean, high-quality code.
• 6+ years of experience in a software engineering role.
• Experience leading projects and being accountable for their outcomes.
• Experience mentoring team members or driving initiatives that help the team learn new skills.
• Experience conducting code reviews and running a robust testing cycle.
• Experience working in agile, fast-paced environments.
• Proficient in Python and modern web stack components such as FastAPI, Django, MySQL, Postgres.
• Experience working in cloud environments (AWS preferred).
• You’ve already experimented with AI in work or personal projects, and you’re excited to dive in and learn fast. You’re hungry to responsibly explore new AI tools and workflows, finding ways to make your work smarter and more efficient.

Nice to have

• Prior work experience with AI tools such as Arize, Langgraph, Langchain.
• Prior work experience building with LLMs such as GPT, Gemini, Claude.