Backend Engineer – ML-Powered Recommendations

Klaviyo; Boston, Northern (MA, KY); Hybrid; USD 116,000 - 174,000; Full time

Job summary

Klaviyo in Boston is seeking a Software Engineer II for Recommendations, onsite 5x a week. You will help build scalable backend services, data pipelines, and ML-enabled features to personalize experiences across channels.

The role emphasizes reliability, observability, and collaboration with ML engineers and product stakeholders. You will own features end-to-end, contribute to the vector search stack, and participate in on-call activities to improve system resilience and performance.

Qualifications

• 2+ years of professional software engineering experience with backend and distributed systems, focusing on latency, reliability, and operability.
• Proficient in Python and open to other languages.
• Experience with cloud-native architectures (AWS) and Kubernetes, including CI/CD pipelines.
• Experience in data-driven decision making and A/B testing; instrumental experiments and learning from results.
• Comfortable designing and querying data models in relational, analytical, and NoSQL stores.
• Strong DevOps practices mindset and ownership of features end-to-end.

Responsibilities

• Contribute to the architecture and evolution of backend services powering product recommendations across Klaviyo experiences.
• Maintain large-scale data processing pipelines transforming raw events into high-quality features for models.
• Collaborate with ML engineers and stakeholders to productionize recommendation models and define interfaces.
• Contribute to vector database development for recommendation, semantic search, and agentic use cases.
• Ensure observability with metrics, logging, tracing, and dashboards for reliable performance.
• Break down projects into milestones with rapid experimentation and long-term maintainability.

Skills

Python

AWS

Kubernetes

Backend systems

Data pipelines

A/B testing

Distributed systems

Communication

AI experimentation

Tools

PostgreSQL

MySQL

Data warehouses

Redis

Vector databases

Job description

Klaviyo in Boston is seeking a Software Engineer II for Recommendations, onsite 5x a week. You will help build scalable backend services, data pipelines, and ML-enabled features to personalize experiences across channels.

The role emphasizes reliability, observability, and collaboration with ML engineers and product stakeholders. You will own features end-to-end, contribute to the vector search stack, and participate in on-call activities to improve system resilience and performance.