Principal Infrastructure Engineer

Join Sezzle as a Principal Infrastructure Engineer, where you will design, build, operate, and scale the platform that powers our business. You will own complex technical initiatives, improve reliability and performance, and connect infrastructure decisions to better customer outcomes and business performance. You will work closely with application engineers, Security, and Compliance, and have a deep understanding of how Sezzle's business operates.

About Sezzle

• You build and ship: you turn architecture into working code, tested infrastructure, and safe production changes
• Experience with multi-region architectures, chaos engineering, and failure testing, including the consistency and recovery tradeoffs of distributed data systems

Responsibilities

• Conception, construction, operation, and scaling of the platform that powers Sezzle, focusing on infrastructure problems.
• Ownership of complex technical initiatives from architecture and prototyping through implementation, production rollout, and ongoing operation.
• Building and applying AI-assisted infrastructure and SRE tooling for incident investigation, capacity analysis, runbook automation, and toil reduction.
• 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
• 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
• Experience implementing and testing disaster recovery against defined recovery objectives, including restoring data and validating service recovery
• 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
• Practical experience with observability, load testing, capacity planning, and safe CI/CD practices for shared production infrastructure
• You value simplicity: you choose systems that are understandable, operable, and reduce unnecessary complexity
• You stay accountable for the outcome: you verify that changes work in production and fixes remain effective as the platform scales
• You're not bound by convention – your success lies in developing new ways to do things
• You have relentlessly high standards – 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

Requirements

• You go deep: you investigate how systems behave under load and failure, follow the evidence, and fix underlying causes
• You earn trust – you listen attentively, speak candidly, and treat others respectfully
• 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
• Bachelor's degree in Computer Science or a similar technical field (required)
• 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
• You have backbone; disagree, then commit – you can respectfully challenge decisions when you disagree, have conviction and are tenacious, but once decisions are made, you commit wholly
• You need action – you value calculated risk-taking and understand that speed matters in business
• You measure results: you can explain the impact of your work in availability, latency, capacity, recovery time, cost, or hours of toil removed
• 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
• 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
• Deep expertise with AWS: production experience across compute, IAM, multi-account architectures, and networking, including VPC design and private connectivity
• 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
• You deliver results – you focus on key inputs, deliver quality work on time, and persist despite setbacks
• 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 building AI-assisted incident investigation or operational automation with restricted access, auditable execution, and clear human review points

Preferred

• Experience building internal platform capabilities and self-service tooling, including deployment automation, progressive delivery, and reusable infrastructure components