Senior Infrastructure Security & Operations Engineer

Location: Belgrade Workplace: onsite About Unlimit   Unlimit is a global fintech ecosystem built to eliminate financial borders holding businesses back. The company provides the extensive infrastructure needed to scale globally, integrating payment processing, multi-currency business accounts, BaaS and crypto gateways into a single, intelligent platform.   Across 17 offices globally, Unlimit bridges hyper-local expertise with a high-capacity financial network, giving companies the agility to expand across regions with operational confidence and speed. Driving the evolution of payments, Unlimit is transforming its infrastructure from human-operated fintech into AI-native financial infrastructure — where APIs are consumed by machines, integrations are negotiated by agents, and systems evolve continuously through intelligent automation. Our next users are not only humans. They are AI agents acting on behalf of humans and businesses.   Unlimit serves more than the needs of businesses today; we are building the nervous system for a borderless global economy. What You'll Be Doing As a Senior Infrastructure Security & Operations Engineer, you’ll be a hands-on technical expert responsible for strengthening Unlimit’s infrastructure security and operational cyber defence capabilities. You’ll combine security engineering, detection and response, vulnerability management, and cloud security expertise to protect our technology ecosystem against evolving threats. A major part of this role will involve transforming traditional security operations through AI-powered and agentic automation. You’ll design and build intelligent security workflows, automate investigations and response activities, and continuously improve the effectiveness and efficiency of our cyber defence capabilities. This role is ideal for an experienced infrastructure or security engineer who combines strong systems engineering fundamentals with practical security operations experience, advanced automation skills, and a passion for building modern, AI-driven security solutions. What You’ll Do Own and continuously improve infrastructure security controls across Unlimit’s global technology environment. Operate and enhance internal Security Operations, including security monitoring, alert triage, incident investigation, and response. Develop and maintain detection engineering capabilities, including SIEM correlation rules, detection use cases, log analysis, and security monitoring integrations. Conduct proactive threat hunting and leverage cyber threat intelligence to identify emerging threats and improve defensive capabilities. Lead technical incident response activities, including investigation, containment, remediation, and post-incident improvements. Manage infrastructure vulnerability assessment and remediation processes, including vulnerability scanning, prioritisation, tracking, and validation. Implement and continuously improve infrastructure hardening and security configurations across servers, endpoints, networks, and cloud environments. Develop and maintain security controls across AWS, Kubernetes, and containerised environments. Own and optimise endpoint protection and detection capabilities, including EDR/XDR technologies. Contribute to network security, directory security, and infrastructure security architecture reviews. Administer, integrate, and continuously improve security technologies, including SIEM, EDR/XDR, vulnerability management, and infrastructure security platforms. Coordinate external penetration testing activities within the infrastructure security scope, validate findings, and support remediation. Provide technical support for IT and Information Security audits, including evidence collection, technical control validation, and remediation of identified gaps. Collaborate closely with Infrastructure, DevOps, Engineering, and Application Security teams to implement practical and scalable security improvements. AI & Agentic Security Automation Design, develop, and maintain AI-powered and agentic security automation as a core part of Cyber Security operations. Build autonomous and semi-autonomous workflows for security alert triage, investigation, enrichment, and response. Develop AI-assisted detection engineering, threat hunting, and threat intelligence processing capabilities. Automate vulnerability analysis, risk-based prioritisation, and remediation workflows. Build custom security integrations, automation scripts, and internal security tools using Python, APIs, and modern AI development frameworks. Leverage LLMs and agentic development tools, including Claude, to improve security operations efficiency and engineering productivity. Ensure AI-powered security workflows incorporate appropriate validation, access controls, and human oversight for sensitive or high-impact actions. What We’re Looking For 6+ years of hands-on engineering experience, including at least 4 years in Cyber Security, Infrastructure Security, or Security Operations. Strong technical background in IT infrastructure, systems engineering, cloud engineering, or platform engineering. Proven experience implementing and maintaining infrastructure security controls in complex production environments. Hands-on experience with Security Operations, SIEM, detection engineering, incident response, and threat hunting. Strong understanding of modern cyber attack tactics, techniques, and procedures (TTPs), including MITRE ATT&CK. Practical experience with EDR/XDR, vulnerability management, and security monitoring technologies. Solid understanding of Linux, networking, operating system security, and infrastructure hardening. Experience securing AWS environments, Kubernetes clusters, and containerised workloads. Strong Python development skills and experience building security automation, integrations, and internal tools. Practical experience developing AI-powered and agentic solutions, including LLM integrations, tool orchestration, autonomous workflows, and AI-assisted automation. Experience integrating security controls and automation into infrastructure and DevOps workflows. Ability to independently investigate complex security issues, identify root causes, and implement effective technical solutions. Strong analytical and problem-solving skills, with an engineering-first approach to security. Ability to work independently while collaborating effectively with Infrastructure, DevOps, Engineering, and Security teams. Technical Experience Hands-on experience with several of the following technologies is highly desirable: Security Operations: CrowdStrike, Elastic Security / Elasticsearch, Tenable. Cloud & Infrastructure: AWS, Kubernetes, container technologies, Cloudflare. Engineering & Automation: Python, Terraform, GitLab, REST APIs. AI & Agentic Development: Claude, LLM APIs, agentic frameworks, tool integrations, and AI-powered workflow orchestration. Nice to Have Previous experience in fintech, financial services, payments, or large-scale regulated e-commerce environments. Experience building AI-powered SOC capabilities or autonomous security operations workflows. Experience developing custom detection rules, security integrations, or open-source security tools. Knowledge of infrastructure security architecture and secure cloud design. Experience with offensive security techniques, infrastructure penetration testing, or adversary simulation. Relevant security, cloud, or engineering certifications. Join Unlimit Team now!   Unlimit is an equal opportunity employer. We believe passionately that employing a diverse workforce is central to our success. We make recruiting decisions based on your experience and skills. We welcome applications from all members of society irrespective of age, sex, disability, sexual orientation, race, religion or belief.