Senior Software Engineer - Devx

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 klaviyo.com/careers to see how we empower creators to own their own destiny.

Klaviyo is growing fast and we have openings for all skill levels across all of our teams. Learn more about our engineering culture at https://klaviyo.tech

We love tackling tough engineering problems and look for Engineers who specialize in certain areas but are passionate about building, owning & scaling features end to end from scratch and breaking through any obstacle or technical challenge in their way. We push each other to move out of our comfort zone, learn new technologies and work hard to ensure each day is better than the last.

Klaviyo operates a real-time data platform coded in Python built for massive scale on Amazon Web Services (AWS). Engineers come to Klaviyo with experience in a variety of languages and from a number of disciplines.

Team Overview:

DevX is a hybrid product–platform team focused on empowering external developers and partners by supporting applications they build on top of Klaviyo’s Public APIs and features. Examples of these areas of ownership include:

• our Application directory, which is used to promote and allow Klaviyo customers to discover applications that they can enable for their account
• the self-serve application process for a Partner to submit an Application and the ability for Klaviyo staff to review and approve an Application
• API Analytics is a system used by developers and partners to diagnose issues in their applications and understand their API usage. It is powered by a near real–time data pipeline that processes over 160,000 events per second.
• Autogenerated API docs, SDKs, CLIs & MCP servers

Responsibilities:

You will have an opportunity to make a major impact on the direction and priorities of the team.

As an engineer on this team, you will work on Klaviyo’s app marketplace, application publishing workflows, and the developer-facing tools and systems that support our app ecosystem. Additional responsibilities include providing quality PR reviews for our code-owned areas of the application, collaborating with product owners and providing technical expertise on upcoming Product Specifications, and participating in the definition of well-defined, estimated, and planned scopes of work.

Required Skills:

• 5+ years of experience in a software engineering discipline
• Experience with full stack application development
• Experience working with both monolithic and microservi