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.

Klaviyo is growing fast and we have openings for all skill levels across all of our teams. 

The mission of the Application Security (AppSec) team is to provide best in class tooling for account management and authorization, and data security and integrity to protect the data of our 250,000+ customers and the data they own across their ecosystem. 

The Appsec team focuses heavily on the backend development and service architecture for our authentication & authorization services, including identity and access management, logging and auditing, single sign-on, and role based access controls. Along with the services, we own the frontend experience for these features and bring a customer-focused approach to balancing customer ease of use and clear UX experiences with each security feature we release. 

As a Senior Software Engineer, you will be responsible for the ownership of key features within the security space, working alongside other experienced engineers while mentoring junior engineers as well. You will work directly with the team and our product manager to help drive technical conclusions from stakeholders, as well as set our roadmap, team objectives, and goals. 

How You’ll Make a Difference

  • Ship foundational services to improve Klaviyo security and enable Klaviyo engineering to release more secure services with confidence
  • Help set alignment on goals, objectives, and technical direction for upcoming features and roadmap planning
  • Design and develop systems and processes that continually increase velocity within the team and our areas of ownership
  • Leverage technology such as Python, AWS, Django, Kubernetes, Bash, Terraform, MySQL, RabbitMQ, Redis, Cassandra, Postgresql to advance Klaviyo’s platform
  • Champion best practices by actively collaborating with other teams in a culture that values whiteboarding and technical design review
  • Contribute to the company as a subject matter expert in multiple areas, constantly pushing yourself to be a better engineer and to level up all of your peers within your team and within Klaviyo.
  • Mentor and pair with other Klaviyo engineers to build better software by focusing on performance, self-healing system, configuration as code; defensive programming, application security, etc.
  • Participate in periodic on call duties with a focus on solving issues when they are discovered, preventing recurrences and minimizing alert fatigue 
  • Prototype and advocate for architectural improvements to achieve breakthrough results in Klaviyo systems’ operational scalability and reliability
  • Work hand-in-hand with customer facing roles such as our sales and support teams, along with the teams Product Manager, to ship high value features.
  • Confidently make informed, data-driven decisions in a fast paced environment with competing priorities

Who You Are

  • 3-5+ years of experience in a software engineering discipline
  • Significant experience with full stack application development and systems administration
  • Experience working with both monolithic and microservices architectures
  • Experience administering cloud-based infrastructure (e.g. AWS)
  • Experience debugging performance issues and production bottlenecks to improve application performance
  • Ability and willingness to learn
  • Ability to communicate clearly and mentor and coach others on a team
  • Ability to participate in an on-call rotation
  • Preferred:
    • Previous experience in a relevant security focused product or company 
    • Experience working with common identity provider vendors, building authorization and authentication features or platforms.
    • Experience leading projects across multiple teams or quarters

Technologies we use (not exhaustive):

Python, Django, React, RabbitMQ, Celery, MySQL, Redis, Memcached

Amazon Web Services (EC2, RDS, Aurora, etc.), Terraform, Jenkins


Get to Know Klaviyo

Klaviyo is a world-leading marketing automation platform dedicated to accelerating revenue and customer connection for online businesses. Klaviyo makes it easy to store, access, analyze and use transactional and behavioral data to power highly-targeted customer and prospect communications. The company's hybrid customer-data and marketing-platform model allows companies to grow by fostering direct relationships with customers, without giving up their valuable data to popular big-tech ad platforms. Over 265,000 innovative companies like Unilever, Custom Ink, Living Proof and Huckberry sell more with Klaviyo. Learn more at

Klaviyo is committed to diversity and to a policy of equal employment opportunity and non-discrimination. We do not discriminate on the basis of race, color, religion, national origin, age, sex, marital status, ancestry, physical or mental disability, veteran status, gender identity, sexual orientation or any other characteristic protected by applicable law.

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At Klaviyo, we strive to make the world more equitable - it’s one of our core values. Klaviyos (our employees) believe that everyone deserves a fair shot at success. We strive to be a diverse company, where we seek opinions and experiences different from our own. Individuals seeking employment at Klaviyo are considered without regard to race, color, religion, national origin, age, sex, marital status, ancestry, physical or mental disability, veteran status, gender identity, sexual orientation or any other characteristic protected by applicable law. 

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