Bartosz Kruszelnicki
Senior Technical Engineer | Senior Middleware & Integration Specialist
Experience
Senior Middleware & SRE Engineer — Instant Payments 2.0 @ Worldline
October 2018 – Present
Progressed from junior to senior within the Instant Payments 2.0 program,
managing dozens of environments and client integrations in a 24/7, high-availability payments ecosystem.
Core stack: RHEL (Linux), JBoss EAP, Tomcat, AMQ,
databases, load balancers, networking and security.
Key responsibilities & achievements
- Owned full lifecycle of enterprise JBoss & AMQ environments:
provisioning, configuration, version management across environments,
client onboarding and connectivity setup, security & certificate management.
- Deployed and maintained JBoss and Tomcat application servers,
handling application packaging, deployment pipelines and lifecycle management
across test, staging and production environments.
- Designed and built complete AMQ infrastructures ensuring reliable messaging
and integration for multiple business clients.
- Planned and implemented environment provisioning:
request & sizing of compute (CPU/memory), storage and network resources (VLANs, firewalls, load balancer rules)
to fit business and compliance requirements.
- Drove security hardening and compliance: TLS/cert management,
OS & middleware baselines, vulnerability remediation, audit readiness.
- Automation & IaC: Bash & Python tooling,
Ansible for configuration management, Terraform for cloud/platform resources.
- CI/CD: pipelines with Jenkins and XL Deploy
(artifact promotion, blue/green & rolling strategies).
For personal projects I prefer GitLab CI over Jenkins.
- Production operations (24/7): incident response, root cause analysis,
capacity/availability planning, Java performance tuning (GC, heap, threads).
- Developed ad-hoc Java applications to handle edge cases,
e.g. migration support or client-specific integration workarounds.
- Identity & integration: LDAP/SSO support (OpenLDAP/389-ds),
certificate lifecycle, compliance with security frameworks.
- Stakeholder leadership: SPOC for major clients, mentoring juniors,
leading interviews, running knowledge-sharing sessions.
LINUX eg Redhat 7+, Ubuntu (cert RHCSA)
LDAP systems: OpenLDAP & 389-ds
Previous Experience
Throughout my high school years (2011 - 2014) at MAK-NET [Internet Service Provider], I served as a technical support specialist. My role encompassed a range of responsibilities, from configuring network devices to installing antennas and links, addressing clients' device issues, and troubleshooting connection hiccups. This multifaceted role immersed me in the intricacies of UNIX-based network infrastructure, particularly with the MIKROTIK variation, enhancing my expertise in this domain.
minor experience
between elementary school and starting university, I operated my own IT service venture, specializing in tasks like OS reinstalls doing some kind of SPA for devices. that time I initially engaged with LINUX/UNIX systems.
Education
Wrocław University of Science and Technology (2014 - 2018)
Bachelor of Science in Systems Engineering with specialization in control systems
Systems Engineering with
specialization of control systems
was great mixture of mentioned
technologies in folowing areas:
IT:
including programming, DB, app design, OS knowledge
Automation & Robotics:
Mainly in programming area, great example might be creating
soft for lifts that control engine.
Al:
machine learning algorithms for example face
recognition, classifying texts
High School nr 1 in Kępno (2010 - 2014)
Specialization in Information Technology: Operating Systems and Computer Networks
Certificates & Trainings
- EX280 (Red Hat Certified Specialist in OpenShift Administration)
- GOOGLE CLOUD - Associate Cloud Engineer Certification
- RHCSA (Red Hat Certified System Administrator)
- JBOSS, APACHE, TOMCAT [one-week workshop]
About Me
My journey with ATOS started with a student internship. After getting an offer to join full-time and being part of the Instant Payments 2.0 project, I found a great fit for my passion for IT. I'm into tech and economics, so I spend a lot of my free time reading and learning new stuff. Oh, and I love hanging out with my two awesome parrots!
Contact Information
Email: bartosz.kruszelnicki1@gmail.com
Phone: +48 537-565-469
Home Lab Projects
Home Workstation: Virtualized Network Infrastructure
As a personal project on my home workstation, I developed a fully virtualized network infrastructure that serves as a multi-functional environment for various IT services. Here’s a breakdown of the key elements:
- File Server for Local Network: Set up a dedicated file server for seamless local file sharing across the network.
- Web Servers with Auto-Renewing SSL Certificates: Hosted several websites accessible over the internet, with SSL certificates that automatically renew on a weekly check using Let's Encrypt. All services are available over HTTPS.
- Fedora and Ubuntu Virtual Machines (VMs): Managed over six VMs running either Fedora or Ubuntu. These machines are integrated with LDAP, ensuring unified user management across the entire environment.
- Monitoring with Prometheus, Zabbix, and Grafana: Each VM and the workstation itself are continuously monitored using Prometheus and Zabbix, with Grafana providing real-time dashboards for system metrics such as CPU usage, memory, filesystem status, and CPU clock speed. Additional custom metrics include:
- The number of banned IP addresses (via Fail2Ban).
- Total IP bans, unbanned IPs, and blocked connections.
- LDAP Authentication Across Components: All critical components, including Zabbix, Grafana, Jenkins, and Kubernetes, are secured with centralized LDAP-based authentication, ensuring a consistent user experience.
- Jenkins CI/CD with Kubernetes: Configured Jenkins to build and deploy application images into the Kubernetes clusters running on the VMs. Jenkins itself, along with Kubernetes services, is secured via LDAP credentials.
- Kubernetes Cluster Hosting Websites: The Kubernetes cluster manages and hosts these websites and several others, leveraging a proxy and ingress for efficient traffic routing and load balancing between the hosted services.
- Fail2Ban Security Layer: To enhance security, the workstation is open to the internet and secured with Fail2Ban, which automatically bans IP addresses after two failed login attempts, with a ban duration of 48 hours.
- Secure Communication: All communications between services (HTTPS, LDAPS) are encrypted to ensure the confidentiality and integrity of data.
This project showcases my ability to build and manage a complex virtualized infrastructure with strong security, monitoring, and automated workflows, using technologies such as Kubernetes, Jenkins, Prometheus, Grafana, Zabbix, and LDAP.
