Software Engineer II - API
Klaviyo
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.
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, 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:
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Public API Framework: Building consistent, reliable, and performant public APIs.
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Internal API Platform: A standardized platform for building, deploying, and consuming internal APIs to accelerate development and improve reliability.
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Encoded Objects: Standardized data schema definition and serialization framework ensuring consistency and compatibility across systems.
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API Rate Limiter: System enforcing request limits to protect API reliability and performance.
Responsibilities:
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Contribute to the evolution of Klaviyo’s public and internal API platforms.
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Participate in code reviews, product specifications, and scope definition.
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Collaborate with product owners and engineering peers to deliver high-quality, scalable solutions.
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Influence the direction and priorities of the API team.
Required Skills:
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3–5+ years of experience in software engineering.
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Experience working with both monolithic and microservices architectures.
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Experience with CI/CD pipelines.
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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:
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Experience with metaprogramming.
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Experience with Go.
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Familiarity with JSON:API.
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Experience designing and building internal or public APIs.
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Experience with Service-Oriented Architecture (preferably in Python).
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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
Massachusetts Applicants:
It is unlawful in Massachusetts to require or administer a lie detector test as a condition of employment or continued employment. An employer who violates this law shall be subject to criminal penalties and civil liability.
Our salary range reflects the cost of labor across various U.S. geographic markets. The range displayed below reflects the minimum and maximum target salaries for the position across all our US locations. The base salary offered for this position is determined by several factors, including the applicant’s job-related skills, relevant experience, education or training, and work location.
In addition to base salary, our total compensation package may include participation in the company’s annual cash bonus plan, variable compensation (OTE) for sales and customer success roles, equity, sign-on payments, and a comprehensive range of health, welfare, and wellbeing benefits based on eligibility.
Your recruiter can provide more details about the specific salary/OTE range for your preferred location during the hiring process.
Get to Know Klaviyo
We’re Klaviyo (pronounced clay-vee-oh). We empower creators to own their destiny by making first-party data accessible and actionable like never before. We see limitless potential for the technology we’re developing to nurture personalized experiences in ecommerce and beyond. To reach our goals, we need our own crew of remarkable creators—ambitious and collaborative teammates who stay focused on our north star: delighting our customers. If you’re ready to do the best work of your career, where you’ll be welcomed as your whole self from day one and supported with generous benefits, we hope you’ll join us.
AI fluency at Klaviyo includes responsible use of AI (including privacy, security, bias awareness, and human-in-the-loop). We provide accommodations as needed.
By participating in Klaviyo’s interview process, you acknowledge that you have read, understood, and will adhere to our Guidelines for using AI in the Klaviyo interview Process. For more information about how we process your personal data, see our Job Applicant Privacy Notice.
Klaviyo is committed to a policy of equal opportunity and non-discrimination. We do not discriminate on the basis of race, ethnicity, citizenship, national origin, color, religion or religious creed, age, sex (including pregnancy), gender identity, sexual orientation, physical or mental disability, veteran or active military status, marital status, criminal record, genetics, retaliation, sexual harassment or any other characteristic protected by applicable law.