Senior Software Engineer, Asynchronous Processing

At Klaviyo, we value the unique backgrounds, experiences and perspectives each team member brings to our workplace. We believe everyone deserves a fair shot at success and appreciate experiences beyond traditional job requirements. If you’re a close but not exact match with the description, we hope you’ll still consider applying.

About the role

The Asynchronous Processing team designs, builds, and operates Klaviyo’s high-scale, event-driven backbone so every product team can reliably move data through our systems with confidence, regardless of volume. By providing opinionated, self-service platforms for queueing and background processing—grounded in technologies like Golang, Python, Apache Pulsar, Kafka, SQS, AWS, and Kubernetes—we enable engineering teams to focus on customer impact while ensuring their workloads are fast, observable, cost-efficient, and resilient by default.

As a Senior Platform Engineer on the Asynchronous Processing team, you will architect, build, and operate the large-scale, event-driven backbone that powers Klaviyo. You’ll design and evolve resilient, multi-tenant queueing and processing platforms that safely handle massive traffic spikes, process millions of messages per second with low latency, and provide simple, self-service APIs and tooling. From core data models and routing patterns to observability, autoscaling, and failure isolation, you’ll own systems that must be rock-solid at scale, partnering closely with engineers across the company to turn complex distributed-systems problems into intuitive, reliable building blocks.

This role is for senior engineers who love taming large-scale distributed systems and turning real-world asynchronous workloads into reliable, scalable platforms. You’ll work on highly visible infrastructure at the heart of Klaviyo’s event-driven backbone, directly shaping how thousands of engineers build, ship, and operate products every day.

Responsibilities

• Build a deep understanding of engineering needs across the organization, guiding the design and development of appropriate platform primitives in queueing that align with the platform's vision and empower product teams.
• Design, develop, and deliver software to dramatically improve the availability, scalability, latency, and efficiency of Klaviyo's asynchronous and queueing services.
• Design and develop systems and processes that enable highly available and scalable systems, with a focus on asynchronous processing.
• Leverage technology such as Python, Golang, AWS, and Kubernetes to advance Klaviyo's platform, with a deep focus on Apache Pulsar, SQS, and Kafka.
• Champion best practices by actively collaborating with other teams in a culture that values technical design review.
• Mentor and pair with other Klaviyo engineers to build better software by focusing on performance, self-healing systems, configuration as code, and defensive programming.
• Participate in periodic on-call duties with a focus on solving issues when they are discovered, preventing recurrences, and minimizing alert fatigue.

Requirements

• Passion for building software effectively and for the long term, balancing technical quality, velocity, and business impact.
• BA or BS Degree in Computer Science, related field, or equivalent experience.
• 6+ years of hands-on software development experience building and operating highly available, full-stack SaaS products at scale, or demonstrated equivalent proficiency and impact.
• Independently responsible for the full lifecycle of complex projects or features, including discovery, technical design, implementation, rollout, and ongoing maintenance. You provide clear technical direction for others involved.
• Own the operational health of the systems you build, including performance, reliability, and observability. Comfortable defining and upholding SLOs, participating in on-call, and driving follow-through on incidents and RCAs.
• Familiarity with cloud infrastructure (AWS preferred), infrastructure-as-code (Terraform), and containerized environments (Kubernetes), including how to design services that run reliably at scale in those environments.
• Expertise and hands-on experience with asynchronous processing and queueing systems like SQS, Kafka, or Apache Pulsar.
• Ability to handle complex systems in outage situations and drive failures to root cause analysis and prevention.
• Experience experimenting with AI in work or personal projects, with excitement to dive in, learn fast, and explore new AI tools and workflows responsibly.
• Question convention and proactively look for ways to improve workflows, architecture, tooling, or team processes. Intrinsically motivated to drive incremental and step-change improvements that deliver business value.
• Excellent communicator and collaborator. Lead technical discussions at the project and product-area level, write clear technical design documents and RFCs, and keep stakeholders aligned on progress, risks, and trade-offs.
• Mentor and support other engineers, offering thoughtful feedback in design and code reviews, helping refine specifications, and investing in the growth of more junior engineers.
• Enjoy working on small, autonomous, agile teams, shipping early and often, pairing with product managers, business stakeholders, and other engineers to craft better software.

Nice to have

• Fundamental understanding of Linux and all layers of the networking stack; confident administering and debugging production Linux systems.
• Practical experience building high availability systems at scale with Apache Pulsar.

Technologies we use

Klaviyo’s platform is primarily built with Python and React and runs on AWS. Engineers join us from a wide range of technical backgrounds and are supported in learning our stack. Core technologies include:

• Python / Django / FastAPI / GoLang
• Protobuf
• Apache Pulsar / Apache Kafka / SQS
• AWS / Terraform / Kubernetes / Argo / Istio / Kong

Location & work model

This role is based in Boston, Massachusetts. Klaviyo supports work authorization and relocation for this position.

Pay

Our salary range reflects the cost of labor across various U.S. geographic markets. 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. The range displayed below reflects the minimum and maximum target salaries for the position across all U.S. locations.

Base pay range for U.S. locations: $148,000—$222,000 USD.

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.

Schedule

This role may require up to 10% travel for purposes such as new hire onboarding, client or partner work (if applicable), team meetings, and industry events. Travel is coordinated in advance.