Lead Software Engineer, Mobile Channels

The Mobile Channels team at Klaviyo powers text messaging across Klaviyo's platform — SMS, RCS, WhatsApp, and a growing set of future text messaging channels. As brands increasingly rely on mobile to reach their customers, our team builds the infrastructure that makes high-throughput, reliable delivery possible across a complex, multi-channel landscape. We own the systems that connect Klaviyo customers to their audiences through the fastest and most personal communication channels available.

As a Lead Software Engineer on the Mobile Channels team, you'll provide technical leadership to a group of engineers building and scaling the services that power Klaviyo's mobile messaging pipeline end-to-end. You'll drive technical strategy, own critical components of the delivery infrastructure, and help the team navigate the unique challenges of multi-channel compliance, carrier regulations, provider integrations, and global deliverability. This is a hands-on technical leadership role where you'll contribute to architecture, code, and mentorship while shaping the future of mobile messaging at Klaviyo.

If you're excited about building systems that deliver millions of messages across channels with speed and reliability — and leading a team at the center of one of Klaviyo's fastest-growing product areas — Mobile Channels is the place to do it.

• Lead a team of engineers building and scaling Klaviyo's mobile messaging infrastructure across SMS, RCS, WhatsApp, and future channels
• Own and drive the architecture of key components in the mobile messaging pipeline — from message ingestion and routing to provider delivery and status tracking
• Design and implement scalable, high-throughput services in Python and Go
• Build systems that ensure reliable delivery at scale while managing carrier compliance, opt-in/opt-out requirements, throughput limits, and international messaging regulations
• Contribute directly to architecture and code, driving best practices and quality
• Collaborate cross-functionally with product, deliverability, compliance, and platform teams to expand mobile channel capabilities
• Grow and mentor engineers while helping shape the future of mobile messaging at Klaviyo
• Transform workflows by putting AI at the center, building smarter systems and ways of working from the ground up

• 8+ years of engineering experience with strong backend and systems design skills
• Proficient in Python and/or Go and be able to rapidly learn the other
• Comfortable coding and reviewing complex systems — this is a hands-on role
• Experienced working with high-throughput distributed systems
• Skilled in system design and scaling infrastructure using AWS
• Strong business and product mindset — you think beyond the code to understand customer impact and commercial value
• Able to bring clarity to ambiguous requirements, breaking down undefined problems into actionable plans
• Self-led and driven to deliver incrementally — you ship value early and iterate
• Bonus: Experience with SMS/MMS infrastructure, RCS, WhatsApp Business API, carrier integrations, telecom APIs, or messaging compliance
• Clear communicator and collaborative team player
• Able to thrive in a hybrid team and deliver in a high-autonomy environment
• 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.

• Python, Go
• AWS, Terraform, DynamoDB, Redis, SQL
• Kafka

This is a hybrid role based in Boston, with 3 days in office and 2 days remote per week.

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.