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.

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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 product ionize 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.

• 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 gates that accelerate—not block—delivery; drive incident deep dives tied to systemic fixes.
• Communicate clearly to execs and engineers, tying technical work to business impact and customer outcomes.
• Integrate AI into scale and resiliency work—from proactive anomaly detection to synthetic load and guided runbooks—so performance improvements stick and incidents don’t repeat.

• Experience:
  
  12+ years scaling multi‑tenant SaaS with a reputation for removing major bottlenecks and proving impact with data.
• Technical expertise:
  Performance engineering, capacity planning, sharding/partitioning, caching/back‑pressure, multi‑region readiness, and high‑volume migrations; you turn hotspots into robust patterns.
• AI tools & automation:
  You apply AI to scale work—profiling assistance, workload modeling, synthetic traffic generation, anomaly detection, and runbook copilots—always with explicit guardrails and observability.
• Cross‑org influence:
  You align teams through fitness functions, scorecards, and readiness gates that accelerate—not block—delivery; you communicate tradeoffs crisply to execs and engineers.
• AI fluency:
  Curious, adaptable, and proactive in exploring AI that responsibly improves scale outcomes.

• Scale scorecard:
  Company‑wide fitness functions (latency/throughput/error rates) are adopted and reviewed regularly.
• High‑impact wins: 2–3 bottlenecks removed with documented, reproducible testbeds; pXX latencies and error rates improve on top enterprise workloads; repeat P0s trend down.
• AI‑assisted scale engineering: AI‑driven anomaly detection reduces alert noise while improving signal; generative load testing and copilot runbooks are used in release/readiness checks for the top critical services; time‑to‑isolate regressions drops 20–30%.

• Company‑wide scale scorecard in place; 2–3 high‑impact bottlenecks removed; top enterprise workloads show improved pXX latencies and error rates; fewer repeat P0s.

Base pay range for US locations: $244,000—$366,000 USD per year.

Our total compensation package may include participation in the company’s annual cash bonus plan, variable compensation (OTE) for sales and customer success roles, equity, sign‑on payments, and a comprehensive range of health, welfare, and wellbeing benefits based on eligibility.

Travel may be required up to 10% of the time for new hire onboarding, client or partner work, team meetings, and industry events.

Massachusetts Applicants:
It is unlawful in Massachusetts to require or administer a lie detector test as a condition of employment or continued employment. An employer who violates this law shall be subject to criminal penalties and civil liability.

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.