Principal Software Engineer, Enterprise Scalability

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. Be Klaviyo’s senior IC for scale, you will report into a VP of Engineering and lead performance, reliability, multi‑region, and large‑tenant readiness. You’ll drive platform-wide architectural change, hunt bottlenecks and optimize systems, and partner across teams to productionize improvements. Given that this is an IC role with no direct reports; you will lead via technical depth, hands‑on impact, and crisp cross‑org alignment. What You’ll Do Define enterprise scalability fitness functions (latency/throughput/error rates) and a scorecard; align teams to SLOs and budgets. Design/implement sharding and partitioning strategies, caching/back‑pressure, multi‑region readiness, and high‑volume migration paths. Build lightweight enablement: benchmarks, profiling harnesses, reproducible testbeds; pair with teams to land fixes. Lead scalability reviews and readiness g...