Principal Infrastructure Engineer

Join Sezzle as a Principal Infrastructure Engineer, where you'll design, build, operate, and scale the platform that powers our business. You'll tackle complex technical initiatives, improve reliability and performance, and connect infrastructure decisions to better customer outcomes. This role requires deep expertise in AWS, Kubernetes, and relational databases, as well as a strong background in infrastructure, platform, and site reliability engineering.

Design, build, operate, and scale the platform that powers Sezzle, focusing on infrastructure problems such as increasing throughput and reducing latency.

About Sezzle

• You deliver results – you focus on the key inputs and deliver them with the right quality and in a timely fashion. Despite setbacks, you rise to the occasion and never settle
• Experience building internal platform capabilities and self-service tooling, including deployment automation, progressive delivery, and reusable infrastructure components

Responsibilities

• Own complex technical initiatives from architecture and prototyping through implementation, production rollout, and ongoing operation, delivering measurable improvements in reliability and performance.
• Participate in the on-call rotation and take a hands-on role in recovering from major incidents, using evidence-based triage and implementing corrective actions.
• You earn trust – you listen attentively, speak candidly, and treat others respectfully
• You measure results: you can explain the impact of your work in availability, latency, capacity, recovery time, cost, or hours of toil removed
• Active use of AI tooling in engineering or operations, with practical judgment about its limitations and how to verify generated code, recommendations, and operational actions
• Experience implementing and testing disaster recovery against defined recovery objectives, including restoring data and validating service recovery
• Deep expertise with relational databases at scale, specifically RDS/Aurora (MySQL and/or Postgres): query performance, indexing, connection management, replication, high availability, failover, and verified backup and recovery
• A track record of personally delivering infrastructure scaling improvements: identifying constraints, measuring baseline behavior, implementing changes, and demonstrating gains in capacity, latency, reliability, or cost efficiency
• You build and ship: you turn architecture into working code, tested infrastructure, and safe production changes
• You value simplicity: you choose systems that are understandable, operable, and appropriate to the problem, and reduce unnecessary complexity

Requirements

• You have backbone; disagree, then commit – you can respectfully challenge decisions when you disagree, even when doing so is uncomfortable or exhausting. You have conviction and are tenacious. You do not compromise for the sake of social cohesion. Once a decision is determined, you commit wholly
• Deep expertise with AWS: production experience across compute, IAM, multi-account architectures, and networking, including VPC design and private connectivity
• You go deep: you investigate how systems behave under load and failure, follow the evidence, and fix underlying causes
• Strong systems fundamentals: Linux, networking, DNS, TLS, storage, concurrency, and distributed system failure modes, with the ability to debug problems across infrastructure and application boundaries
• Practical experience with observability, load testing, capacity planning, and safe CI/CD practices for shared production infrastructure
• Strong coding and automation skills, using Golang, Python, or similar languages to build production tooling and eliminate operational toil, alongside infrastructure-as-code experience with Terraform or equivalent
• Experience operating a 24/7, high-availability platform where downtime has direct customer or revenue impact, including hands-on incident response and postmortem remediation
• Bachelor's degree in Computer Science or a similar technical field (required)
• You earn trust: you listen carefully, communicate clearly, challenge technical decisions respectfully, and follow through on commitments
• Willingness to participate in an on-call rotation and demonstrated ability to recover production systems under pressure using evidence-based triage, safe mitigation, and clear technical communication
• Deep expertise with Kubernetes in production: cluster lifecycle, scheduling, resource management, autoscaling, networking, and troubleshooting business-critical workloads. EKS experience is strongly preferred
• Ability to carry ambiguous technical problems from investigation through production delivery and collaborate across engineering disciplines to resolve system-wide constraints
• You’re not bound by convention – your success—and much of the fun—lies in developing new ways to do things
• 12+ years of experience across infrastructure, platform, site reliability, software development, or related engineering disciplines, with substantial hands-on depth designing and operating production infrastructure at scale
• You need action – speed matters in business. Many decisions and actions are reversible and do not need extensive study. We value calculated risk-taking
• You have relentlessly high standards – many people may think your standards are unreasonably high. You are continually raising the bar and driving those around you to deliver great results. You make sure that defects do not get sent down the line and that problems are fixed so they stay fixed
• You stay accountable for the outcome: you verify that changes work in production and that fixes remain effective as the platform scales
• Proficiency with Prometheus, Grafana, Loki, Tempo, or comparable observability systems
• Experience in fintech, payments, or banking, operating infrastructure with demanding reliability, security, and audit requirements
• Experience with multi-region architectures, chaos engineering, and failure testing, including the consistency and recovery tradeoffs of distributed data systems
• Experience building AI-assisted incident investigation or operational automation with restricted access, auditable execution, and clear human review points