Senior Software Engineer, Reliability

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. Team Overview: As a Senior Software Engineer, Reliability, you’ll ensure Klaviyo’s critical platforms are reliable, scalable, and sustainable while enabling rapid product development. We treat reliability as a core product feature and use software engineering to solve complex systems and operational challenges. Our work spans security, infrastructure, and software development, requiring us to understand systems and engineering. We build complex, foundational solutions that must be extremely reliable, secure, and performant at global scale. Our charter is to build and operate foundational services and infrastructure, define clear reliability objectives, reduce operational toil through automation, and continuously improve systems based on real production learnings. The work is highly visible and directly impacts how Klaviyos build software and how customers experience Klaviyo every day. How You’ll Make an Impact: As a Senior Software Engineer, Reliability, you will build and operate the platforms, systems, and services that underpin Klaviyo’s reliability and operational excellence. You will: Build and operate foundational, security-critical services with a strong emphasis on availability, scalability, latency, and fault tolerance Apply software engineering principles to automate infrastructure, reduce operational toil, and improve system reliability at scale Design, implement, and evolve systems using SRE best practices Define and refine SLIs, SLOs, and error budgets to guide engineering decisions Improve observability, alerting, and incident response to reduce mean time to detection and recovery Participate in on-call rotations with a focus on sustainable operations and automatic remediations Perform quantitative analysis to understand system behavior, capacity constraints, and scaling limits Identify systemic risks and reliability bottlenecks and drive long-term, preventative solutions Collaborate closely with product, platform, and security engineers to influence architecture early and ship reliable systems Mentor and pair with other engineers, helping raise the bar for reliability, operational maturity, and engineering excellence Who You Are: You are a cloud-native, platform-focused SRE who uses software to build and operate reliable production systems at scale. You write and maintain production-quality code (e.g. Python, Go, or similar) to build internal platforms, automate operations, and improve system reliability You have built, deployed, and operated distributed, cloud-native systems and understand failure modes such as partial outages, dependency failures, resource saturation, and cascading impact You have experience operating containerized workloads and platforms (e.g. Kubernetes) in production, including deployment strategies, scaling behavior, and service networking You are comfortable participating in on-call rotations and diagnosing production issues You have designed and operated observability systems and know how to build actionable alerts that reflect real user and service impact You apply SRE concepts such as SLIs, SLOs, error budgets, and burn-rate–based alerting to guide engineering decisions and operational response You have hands-on experience with infrastructure as code and declarative configuration (e.g. Terraform, Kubernetes manifests, policy-as-code) You have performed capacity planning, load testing, and performance analysis for distributed services and platforms You routinely contribute to post-incident reviews and drive concrete, code-focused follow-up actions that prevent recurrence You are comfortable reviewing and contributing to technical designs, platform APIs, operational runbooks, and system documentation You’ve already experimented with AI in work or personal projects, and you’re excited to dive in and learn fast. You’re hungry to responsibly explore new AI tools and workflows, finding ways to make your work smarter and more efficient. Nice to Have: Experience supporting security-critical platforms or building internal security tooling Familiarity with identity, access management, secrets management, or policy enforcement systems Experience operating systems at scale in cloud environments (AWS preferred) Background in resilience testing, fault injection, or chaos engineering A strong comprehension of algorithms and data structures at scale Tech Stack: 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 MySQL / Redis / Memcached RabbitMQ / Celery / Apache Kafka / Apache Pulsar AWS / Terraform / Kubernetes Our salary range reflects the cost of labour in the country where the job post is advertised. 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. Base Pay Range in Local Currency: €92.000 — €138.000 EUR 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. 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. IMPORTANT NOTICE: Our company takes the security and privacy of job applicants very seriously. We will never ask for payment, bank details, or personal financial information as part of the application process. All our legitimate job postings can be found on o