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Klaviyo is a leading marketing automation platform empowering creators and businesses to deliver personalized customer experiences at scale. The Messaging Infra organization builds mission-critical, event-driven systems responsible for delivering billions of real-time, low-latency messages across multiple channels including email, SMS/MMS/RCS, mobile push, and WhatsApp.
In this Senior Software Engineer role, you will design and build highly-available, low-latency, high-throughput event-driven services processing live messaging events. You'll work on Klaviyo's real-time messaging pipeline, which currently processes hundreds of millions of messages daily and is scaling toward billions, where performance and reliability directly impact whether customers receive messages on time.
Key responsibilities include: designing and implementing backend services handling real-time traffic, asynchronous processing, queues and streams with careful tradeoffs around throughput, latency, and reliability; owning and evolving components of the scalable campaign pipeline from processing and routing through delivery and status tracking; collaborating across teams on system designs and engineering practices; mentoring other engineers; and contributing as a subject matter expert to continuously improve systems and processes.
You bring 5+ years of professional software engineering experience building and operating online, real-time distributed systems where latency, throughput, and reliable processing matter. You have hands-on experience designing event-driven or asynchronous systems using events, queues, streams, or messaging platforms (Kafka, Pulsar, RabbitMQ, SQS, or similar). You understand large-scale system architecture patterns and their tradeoffs, have deep fluency in at least one backend language (Python, Go, Java, Scala, or similar), and love solving performance and scalability challenges. You're passionate about data-driven product improvement, familiar with system monitoring and alerting, and have proven experience coaching and mentoring team members.
