Senior Full Stack Engineer - New Product

Klaviyo•Boston, MA

1d•Remote

About The Position

Our team is looking for a Senior Full Stack Engineer to lead key initiatives that will enhance our product offerings and support our company’s growth. In this role, you'll play a crucial part in shaping outcomes by developing innovative end-to-end solutions using both front-end and back-end technologies. You’ll optimize existing products and create new solutions that redefine what’s possible for our customers. As a Senior Engineer, you’ll tackle complex challenges, develop multiple solutions, and evaluate business and technical trade-offs to determine the best path forward. You’ll also act as a leader and mentor, and drive key technology decisions. Additionally, you’ll be responsible for deploying well-designed, thoroughly tested solutions that ensure reliability and performance. The New Products team drives Klaviyo’s most ambitious innovations—creating and scaling the company’s boldest new bets. As a nimble group with a flat structure and fast-moving culture, we prioritize simplicity, speed, and impact. Every team member is expected to take radical ownership—rolling up their sleeves, collaborating across disciplines, and pushing beyond traditional role boundaries to make things happen. Success in this role means delivering exceptional work that sets the standard for velocity and results company-wide, while helping shape Klaviyo’s future through experimentation, creativity, and executional excellence. Transform workflows by putting AI at the center, building smarter systems and ways of working from the ground up.

Requirements

A proven track record of building high-quality products and systems, with pride in writing clean, high-quality code.
7+ years of experience in a software engineering role.
Strong experience developing end-to-end software solutions or extensive experience with both front-end and back-end technologies.
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.
Excited to dive in and learn fast about AI.
AI fluency at Klaviyo includes responsible use of AI (including privacy, security, bias awareness, and human-in-the-loop).

Nice To Haves

Skills with Python and related technologies
Skills with React and related technologies
Experience developing digital marketing or customer data software solutions.
Experience with machine learning.
Experience building cloud-native solutions, ideally with AWS.

Responsibilities

Developing innovative end-to-end solutions using both front-end and back-end technologies.
Optimizing existing products and creating new solutions.
Tackling complex challenges, developing multiple solutions, and evaluating business and technical trade-offs.
Acting as a leader and mentor.
Driving key technology decisions.
Deploying well-designed, thoroughly tested solutions that ensure reliability and performance.
Taking radical ownership, collaborating across disciplines, and pushing beyond traditional role boundaries.
Experimenting with AI in work or personal projects.
Responsibly exploring new AI tools and workflows to make work smarter and more efficient.