Software Engineer II - Custom Objects

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.

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Klaviyo operates a real-time data platform built for massive scale, powering segmentation, automation, analytics, and personalization for hundreds of thousands of customers. At the core of this platform are three foundational data entities:
Profiles, Events, and Objects.

The Custom Objects team owns the platform that allows customers to define, store, and evolve their own domain-specific data models — enabling richer personalization, advanced segmentation, and flexible analytics beyond Klaviyo’s built-in data types.

As a Software Engineer II on the Custom Objects team, you’ll help build and scale the systems that allow customers to safely model, query, and activate their custom data at scale.

Custom Objects unlock how customers represent their business inside Klaviyo.

In this role, you’ll:

• Build systems that support customer-defined schemas and flexible data models
• Enable other teams (Flows, Segmentation, Analytics, AI) to safely rely on object data
• Work on platform primitives that must balance flexibility, correctness, performance, and cost
• Contribute to a core data surface that directly impacts customer experience and product velocity

• Design, build, and maintain services that power the Custom Objects platform
• Implement APIs and data pipelines for creating, updating, and querying custom object data
• Work with evolving schemas while maintaining backwards compatibility and data integrity
• Collaborate with Product, Events, Profiles, and Analytics teams to integrate custom objects into the broader platform
• Debug and improve performance of data-heavy systems operating at scale
• Participate in code reviews, design discussions, and on-call rotations
• Contribute to improving operational excellence through better observability and tooling

• 3–6 years of professional software engineering experience
• Experience building backend systems in a production environment
• Strong fundamentals in data structures, algorithms, and system design
• Experience working with databases or data storage systems (relational or distributed)
• Ability to reason about correctness, tradeoffs, and edge cases in stateful systems
• Strong communication skills and comfort working with cross-functional partners

• Experience with schema-driven or user-defined data models
• Familiarity with distributed systems and high-throughput services
• Experience working with Python or similar backend languages
• Exposure to cloud infrastructure (AWS preferred)
• Experience supporting both online and analytical workloads

• Develop a strong understanding of Klaviyo’s data model and platform architecture
• Contribute meaningful code to production systems
• Learn how custom objects interact with Events, Profiles, and downstream consumers
• Participate effectively in design and code reviews

• Own medium-sized features or system improvements end-to-end
• Improve reliability, performance, or usability of the Custom Objects platform
• Demonstrate strong judgment around data modeling and tradeoffs
• Be a reliable on-call contributor and teammate
• Help raise the overall engineering bar through thoughtful reviews and collaboration

• You’ll work on customer-defined data, one of the hardest classes of platform problems
• You’ll solve challenges around schema evolution, correctness, and scale
• Your work will directly impact how customers model their business and activate their data
• You’ll gain deep experience in platform engineering at the heart of Klaviyo’s data systems

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