Software Engineer II, Verticals​/Integrations

The Integrations team is responsible for building and maintaining Klaviyo’s integrations to a variety of 3rd party vendors. These vendors can be grouped across a number of industries such as ecommerce, point of sale, payment processing, advertising, and fundraising. In order to enable our customers to integrate with these different vendors we provide easy-to-use interfaces that guide our customers through the setup and management of an integration.

Behind the scenes, we use a variety of pipelines to process data flowing to and from these vendors  collaborate closely with internal stakeholders and have substantial exposure to Klaviyo's customers, including businesses, partners, and third‑party developers.

How you’ll make an impact

The Integrations team operates at the intersection of distributed systems, software architecture data mapping & pipelining, scalability, and reliability. As a Software Engineer, you will help us build thousands of integrations across various verticals in a fast, flexible, efficient, and maintainable way, resulting in world‑class customer and developer experiences. Critical components of the Integrations space include Klaviyo’s V3 APIs, 3rd‑party vendor’s APIs, inbound and outbound data pipelines, and data mapping and transformation.

You will have an opportunity to learn our existing end‑to‑end integration workflow and help scale it up to support the next evolution of Klaivyo’s growth into several verticals beyond e‑commerce. You’ll work closely with a team of talented software engineers, data scientists, product managers, and UX/UI designers who are eager to make the process of integrating with Klaviyo fast, efficient, and seamless.

Your skills as a software engineer, outside‑the‑box thinking, and execution will help shape Klaviyo’s trajectory for the next decade.

Who you are

• You are passionate about building software effectively and for the long‑term.
• You have 4+ years of hands‑on software development experience creating and maintaining highly available, full‑stack SaaS products at scale.
• Bachelor’s degree or equivalent.
• A good understanding of the Integrations technical space – 3rd‑party APIs, authentication, storage, and data pipelines.
• You have an in‑depth understanding of commonly used web architecture design patterns when it comes to highly scalable systems.
• You have been a successful interface between the team and the rest of your product area. You have been responsible for owning and delivering projects or features of projects including design, development, and deployment.
• You possess excellent verbal and written communication skills. Through effective proactive communication and planning, you keep your team up to date on project progress and any blockers or delays.
• You like to question convention, proactively find ways to innovate, and are intrinsically motivated to drive incremental improvements that deliver value to the business.
• You like working on small, autonomous agile teams. Enjoy shipping code early and often in an agile fashion, pairing with product management, business stakeholders, and other engineers to craft better software.
• You have a good understanding of popular AI tools (ChatGPT, Claude Code, Cursor, Gemini, etc.) and know how to use them effectively in your own day‑to‑day workflow to increase coding and productivity efficiency.
• You enjoy working with new technologies ranging from the frontend to backend, and are particularly passionate and an expert in various tech stacks.
• Ability to dig into performance and scalability issues to drive breakthrough solutions—whether it's a slow loading UI or too many clicks in a workflow, a database query timing out, or a queue that just won’t drain.
• You like creating, teaching, and improving shared engineering processes.
• You are successfully able to estimate and manage project timelines and risks to ensure the team will be in a position to deliver on its commitments.
• You are proficient in writing technical specifications and documents based on product feature specifications provided by the Product team, and are adept at breaking down and articulating complex technical concepts in a clear and concise manner.
• You are…