Lead Software Engineer - Sending Platform

Klaviyo • Boston, MA

1d • Hybrid

About The Position

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 careers.klaviyo.com to see how we empower creators to own their own destiny.
Why You Should Join the UCM Team:
The UCM (Unified Communication Management) team sits at the core of how Klaviyo delivers messages to customers at massive scale. We own the systems responsible for sending, routing, and processing billions of messages across channels, making UCM a critical pillar of Klaviyo’s platform and customer experience. Our work directly impacts deliverability, reliability, and performance for some of the most business-critical workflows at Klaviyo.
As a Lead Software Engineer on the UCM team, you’ll lead a group of engineers building and operating high-throughput, distributed systems that power message delivery end-to-end. You’ll work deeply in a microservices-oriented architecture, designing resilient, scalable infrastructure that operates at global scale. This is a hands-on leadership role where you’ll contribute to system design, implementation, and technical strategy while mentoring engineers and setting the technical direction for the team.
This role offers a unique opportunity to lead one of Klaviyo’s most foundational platforms—the systems that every message flows through. Your work will shape how we scale globally, improve reliability and performance, and enable faster innovation across product teams. If you’re excited about solving complex distributed systems problems and leading a team at the heart of Klaviyo’s messaging ecosystem, UCM is the place to do it.

Requirements

• 8+ years of engineering experience with strong backend skills (Python or Go or Similar)
• Comfortable coding and reviewing complex systems — this is a hands-on role
• Skilled in system design and scaling infrastructure using AWS
• Clear communicator and collaborative team player
• 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 Haves

• Experience building developer platforms or internal tooling is a strong plus

Responsibilities

• Lead a team of engineers building and evolving Klaviyo’s core messaging and communication platform
• Own message ingestion, routing, processing, and delivery pipelines that handle billions of messages at scale
• Build and operate highly available, distributed systems that support global traffic, reliability, and performance
• Contribute directly to system architecture and code, driving best practices in scalability, resilience, and operational excellence
• Collaborate closely with product, infrastructure, and partner teams to enable new channels, use cases, and platform capabilities
• Grow and mentor engineers while helping shape the future of Klaviyo’s messaging infrastructure
• Transform messaging workflows by putting AI at the center, enabling smarter routing, optimization, and operational decision-making from the ground up

What This Job Offers

• Job Type: Full-time
• Career Level: Mid Level
• Education Level: No Education Listed
• Number of Employees: 501-1,000 employees