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Salary: GBP 68,000 - 102,000 / annual
Klaviyo is seeking a Fullstack Software Engineer II to join the SMS International team within Mobile Platforms. This team is responsible for expanding SMS capabilities into new countries and regions and spearheading the development of RCS (Rich Communication Services) as a new capability alongside existing mobile channels (SMS, Push Notifications, In-App Messages, WhatsApp).
You will work with a team of 4 colleagues to deliver RCS and SMS International expansion to meet company objectives. In this role, you'll build brand new services, understand how they fit into the broader platform architecture, and plan how to architect and scale them to serve over 200,000 ecommerce clients globally.
The Mobile Platforms team focuses on performance optimization and continuous development of mobile marketing channels and SDKs (iOS, Android, React Native). The SMS International team has an ambitious roadmap for 2026-2027 that positions it at the heart of the company's strategic objectives.
Tech Stack: Python, Django, Go, React, RabbitMQ, Celery, MySQL, DynamoDB, Elasticache, Redis, AWS (EC2, RDS, Aurora, SQS), Terraform, Kubernetes, Splunk, Buildkite, Grafana. The team also uses Claude Code and other LLM tools.
The role may require up to 10% travel for onboarding, client/partner work, team meetings, and industry events, coordinated in advance.
Klaviyo empowers creators to own their destiny by making first-party data accessible and actionable. The company emphasizes responsible AI use, including privacy, security, bias awareness, and human-in-the-loop approaches.
REQUIREMENTS:
- 3-5 years of experience in software engineering
- Experience with full stack application development
- Experience working with both monolithic and microservices architectures
- Experience working with AI tools to deliver business outcomes
- Experience with database design that can withstand high query volumes
- Experience with CI/CD pipelines
- Experience debugging performance issues and improving application performance
- Interest and aptitude for collaboration across teams and disciplines
NICE TO HAVE:
- Experience creating new services with scalability in mind; exposure to large-scale system design
- Experience with AWS or similar cloud providers
- Communication domain experience
