Senior System Administrator / L3 Infrastructure Engineer

• Practice Cloud & Infrastructure

• Technologies Infrastructure & Cloud

• Location Zagreb, Croatia

• Type Contract

Senior System Administrator / L3 Infrastructure Engineer

Location: Zagreb, Croatia (On-site)
Contract Duration: 6 Months
Language Requirements: Fluent Croatian and Professional English

Overview

We are seeking an experienced Senior System Administrator / L3 Infrastructure Engineer to join a critical infrastructure and operations team based on-site in Zagreb. This role is suited to a highly skilled infrastructure professional with strong Linux administration expertise, enterprise database knowledge, and extensive experience providing L3 production support within complex environments.

The successful candidate will be responsible for managing, supporting, troubleshooting, and optimising enterprise infrastructure platforms, ensuring high availability, performance, and stability across production systems.

Key Responsibilities

• Provide advanced L3 production support for critical infrastructure and application environments.
• Diagnose and resolve complex technical issues across server, database, network, and application layers.
• Administer and maintain Linux-based systems including Red Hat, CentOS, and Debian.
• Support and optimise enterprise databases including Microsoft SQL Server, PostgreSQL, Oracle, and MongoDB.
• Execute software releases, upgrades, patching, and deployment activities.
• Perform system monitoring, performance analysis, capacity planning, and root cause investigations.
• Support incident, problem, and change management processes within SLA-driven environments.
• Conduct and support performance, load, high availability, security, and validation testing activities.
• Produce and maintain technical documentation, operational procedures, and knowledge base articles.
• Collaborate with development, infrastructure, security, and operations teams to ensure service reliability and continuous improvement.

Required Skills & Experience

Essential

• Fluent Croatian language skills.
• Professional English communication skills.
• Strong Linux administration experience (Red Hat, CentOS, Debian).
• Strong database administration and troubleshooting experience with:
  • Microsoft SQL Server
  • PostgreSQL
  • Oracle Database
  • MongoDB
• Proven experience providing L3 support within production environments.
• Strong analytical and troubleshooting skills.
• Availability to work on-site in Buzin, Zagreb.
• Availability for the full contract period from 2 November 2026 to 30 April 2027.

Important

• Scripting experience using:
  • Python
  • PowerShell
  • Bash
• Windows administration experience:
  • Windows 10/11
  • Windows Server
• Networking knowledge including:
  • TCP/IP
  • HTTP
• Security knowledge, particularly TLS.
• Software release and patch deployment experience.
• Experience with:
  • Load testing
  • Performance testing
  • High Availability (HA) testing
  • Security testing
  • Validation testing
• Experience working within ticketing, incident management, and SLA-driven support environments.

Nice to Have

• VMware
• OpenStack
• Kubernetes
• Monitoring and observability tools:
  • Zabbix
  • Grafana
  • Prometheus
• API testing tools:
  • SOAPUI
  • Postman
• Technical documentation and knowledge management expertise.

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