Software Engineer II - API

Klaviyo is growing fast, and we have openings for all skill levels across all of our teams. Learn more about our engineering culture at .

We love tackling tough engineering problems and look for engineers who specialize in certain areas but are passionate about building, owning, and scaling features end to end — 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.

Location:
This position is based in our Boston office , and team members are expected to be onsite at least three days per week .

Our Stack and Culture:
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:
The API team empowers product development teams at Klaviyo to create consistent, reliable, and developer-friendly public and internal APIs by providing robust frameworks, intuitive tools, and expert support.

Areas of ownership include:

• 
  

  Public API Framework: Building consistent, reliable, and performant public APIs.



• 
  

  Internal API Platform: A standardized platform for building, deploying, and consuming internal APIs to accelerate development and improve reliability.



• 
  

  Encoded Objects: Standardized data schema definition and serialization framework ensuring consistency and compatibility across systems.



• 
  

  API Rate Limiter: System enforcing request limits to protect API reliability and performance.

Responsibilities:

• 
  

  Contribute to the evolution of Klaviyo’s public and internal API platforms.



• 
  

  Participate in code reviews, product specifications, and scope definition.



• 
  

  Collaborate with product owners and engineering peers to deliver high-quality, scalable solutions.



• 
  

  Influence the direction and priorities of the API team.

Required Skills:

• 
  

  3–5+ years of experience in software engineering.



• 
  

  Experience working with both monolithic and microservices architectures.



• 
  

  Experience with CI/CD pipelines.



• 
  

  Strong debugging and performance optimization skills.

Team Tech Stack:
Python, Django REST Framework, Django, FastAPI
MySQL / PostgreSQL, DocumentDB, ClickHouse
Redis, Memcached, RabbitMQ / Celery / Apache Pulsar

Preferred Skills:

• 
  

  Experience with metaprogramming.



• 
  

  Experience with Go.



• 
  

  Familiarity with JSON:API.



• 
  

  Experience designing and building internal or public APIs.



• 
  

  Experience with Service-Oriented Architecture (preferably in Python).



• 
  

  Experience working with RESTful applications, APIs, or gRPC.

We use Covey as part of our hiring and / or promotional process. For jobs or candidates in NYC, certain features may qualify it as an AEDT. As part of the evaluation process we provide Covey with job requirements and candidate submitted applications. We began using Covey Scout for Inbound on April 3, 2025.

Please see the independent bias audit report covering our use of Covey here