Senior Security Infrastructure Engineer

We are seeking a hands-on, high-impact Senior Security Infrastructure Engineer to help strengthen Sezzle’s security posture across cloud infrastructure, applications, and developer workflows. This role is ideal for someone who thrives in a fast-paced environment and wants to work on real-world security problems at scale.

As a Senior Security Infrastructure Engineer, you will have a high degree of ownership and autonomy to identify risks, investigate issues, and drive meaningful security improvements across our systems. You will work across vulnerability management, detection engineering, supply chain security, and incident response - partnering closely with engineering teams to ensure security is practical, effective, and embedded into how we build and operate systems. You should consider yourself a DOer - someone who is comfortable diving into logs, analyzing systems, validating findings, and working end-to-end to get issues resolved. We value engineers who bring strong technical depth, good judgment, and the ability to turn security insights into actionable outcomes.

This role offers the opportunity to shape and scale security capabilities, including detection systems, supply chain risk controls, and security automation. With the support of modern tooling (including AI where appropriate), you will play a key role in improving efficiency, visibility, and resilience across the organization. This role combines hands-on security operations with exploratory and design work. You will spend significant time investigating and resolving real-world issues, while also researching, evaluating, and building new security capabilities across areas like detection, supply chain security, and data protection.

• Lead and operate vulnerability management across infrastructure, platforms, and applications - including internal scans, dependency analysis, and external findings, validating true positives and driving remediation with engineering teams
• Build, operate, and mature SIEM/XDR capabilities, including log ingestion, detection rule development, alert tuning, and investigation workflows
• Investigate and respond to security incidents across cloud infrastructure and applications, performing root cause analysis and driving long-term fixes
• Design and implement detection strategies for suspicious activity, including data exfiltration patterns using application and database telemetry
• Lead and contribute to threat modeling exercises and security design reviews to identify risks early and strengthen architecture
• Apply deep expertise in AWS and Kubernetes to design, secure, and improve resilient and secure cloud infrastructure at scale
• Drive infrastructure and CI/CD hardening initiatives, with a focus on reducing software and container supply chain risk
• Lead efforts to implement and improve dependency and container supply chain risk detection systems and controls
• Partner closely with engineering teams to remediate vulnerabilities and improve secure development and deployment practices
• Support and implement security controls aligned with PCI DSS, SOC 2, and other compliance requirements
• Develop and implement automation (including AI where appropriate) to improve efficiency in security operations, detection, and response
• Triage and validate external security findings, distinguishing true positives and coordinating remediation

What We Look For:

• 6+ years of experience in security, software, or infrastructure engineering, with hands-on experience securing cloud-based production systems and working with real-world security challenges
• Experience contributing to threat modeling and security design reviews for modern systems
• Strong hands-on experience in vulnerability management, including scanning, triage, validation, remediation coordination, and verification
• Experience working with SIEM platforms (e.g., Wazuh, Splunk, ELK) for detection engineering, monitoring, and incident response
• Practical experience triaging findings from vulnerability scanners and bug bounty programs
• Strong knowledge of AWS, Linux, and Kubernetes infrastructure, including security architecture, hardening, and operational best practices
• Experience improving infrastructure security, including CI/CD hardening and mitigating software supply chain risks
• Experience with container and dependency security tools (e.g., Snyk, Trivy, Grype, etc.)
• Ability to investigate issues directly using logs, cloud tooling, and system-level data
• Knowledge of common security vulnerabilities and mitigation strategies (OWASP, SANS, etc.)
• Working knowledge of compliance frameworks such as PCI DSS and SOC 2
• Demonstrated experience working with Claude or equivalent large language model tools is required; candidates must be comfortable leveraging AI to enhance productivity, research, and communication.