# Denys Zhdanov - Senior Site Reliability Engineer | DevOps & Linux Systems Expert
Source: https://hello.cv/denyszhdanov
Amsterdam

## Links
- LinkedIn | http://www.linkedin.com/in/deniszh
- GitHub | http://github.com/deniszh/
- Email
- Phone

## About
Highly accomplished Senior Site Reliability Engineer with over 20 years of expertise in Linux systems, DevOps, and SRE principles, specializing in building and optimizing resilient distributed systems. Proven ability to drive innovation in observability, database management, and cloud infrastructure, consistently delivering high-performance solutions and contributing to open-source projects like Graphite.

## Work
### Senior Site Reliability Engineer | Booking.com
http://www.booking.com
Leading observability initiatives as a Senior SRE, leveraging a diverse technical stack to enhance system reliability and performance for Booking.com.
- Architected and implemented robust observability solutions utilizing AWS, EKS, Mimir, Loki, Grafana, and Prometheus to ensure high availability and performance of critical travel platforms.
- Developed and optimized infrastructure-as-code using Terraform and Python, streamlining deployment processes and improving system scalability.
- Applied FinOps principles to cloud resource management, identifying cost optimization opportunities within Kubernetes (EKS) environments.
- Contributed to Go-based services, enhancing system resilience and operational efficiency within a large-scale distributed architecture.
### Part-time Consultant (Go, Python, Lua Developer) | Circonus, Inc
http://www.circonus.com
Provided specialized consulting services, focusing on Go, Python, and Lua development to enhance monitoring product functionalities.
- Reimplemented Graphite functions in Lua for the IronDB monitoring product, significantly enhancing data processing efficiency and feature set.
- Contributed to core development in Go, Python, and Lua, delivering robust solutions for complex monitoring challenges.
- Collaborated with engineering teams to integrate new features and optimize existing functionalities within the monitoring platform.
### Senior Linux System Engineer / Subject Matter Expert in Databases | Marktplaats B.V. (part of Adevinta SA)
http://www.marktplaats.nl/
Led database and observability initiatives, driving the adoption of new technologies and enhancing infrastructure reliability for a major e-commerce platform.
- Led the company-wide implementation of CockroachDB as a newSQL database solution, significantly improving data scalability and resilience.
- Promoted NoSQL (Cassandra) and NewSQL (CockroachDB) solutions, educating development teams through workshops and classes to foster broader adoption.
- Engineered and executed multiple observability migrations, transitioning Graphite to Metrictank and operational monitoring from Nagios/Graphite to Thanos/Prometheus, enhancing system visibility and performance.
- Designed and improved a Packer-based infrastructure pipeline for VM image building, streamlining deployment processes and ensuring consistency across environments.
- Managed a major MySQL migration project, consolidating sharded clusters back to a single 5.7 instance for simplified management and improved performance.
### Linux System Engineer | Marktplaats B.V. (part of Adevinta SA)
http://www.marktplaats.nl/
Played a key role in infrastructure migration and database optimization projects, enhancing system reliability and performance for an e-commerce platform.
- Participated in multiple migration projects from bare metal to an Openstack-based private cloud, leveraging Hashicorp products and Saltstack for seamless transitions.
- Curated several major MySQL migrations (5.6 to 5.7 and 5.7 to sharded clusters), ensuring data integrity and minimal downtime.
- Optimized the Graphite stack by implementing Grafana and migrating Python Graphite to Go-graphite, significantly improving monitoring performance and visualization capabilities.
- Contributed to infrastructure automation initiatives, reducing manual effort and increasing system reliability.
### Linux Engineer | eCG / Marktplaats B.V.
http://www.marktplaats.nl/
Engineered and supported critical Linux infrastructure, focusing on deployment, database management, and monitoring for a high-traffic e-commerce platform.
- Developed and fixed Fabric-based deployment scripts, integrating with Citrix Netscaler as a load balancer to enhance release efficiency and system stability.
- Managed Riak deployments, including load testing, monitoring, enterprise evaluation, and backup, ensuring high availability and data integrity.
- Executed dotCMS migration from 1.9 to 2.X and subsequently to MySQL 5.6, minimizing service disruption and improving platform performance.
- Enhanced MySQL monitoring and troubleshooting, including Percona XtraDB Cluster evaluation, and led the migration of all production clusters from MySQL 5.1 to 5.6.
- Implemented and supported Graphite monitoring, including deployment, patching, load testing, and migration to a sharded setup, improving observability for critical systems.
### Senior Unix System Administrator/Architect | Cogniance, Inc
http://www.cogniance.com
Provided architectural guidance and operational support for a mobile marketing adserver platform, integrating DevOps principles and optimizing system performance.
- Supported Velti's Adserver platform (RHEL5, Jboss AS, PostgreSQL, Hadoop, Voldemort, AWS), ensuring 24/7 availability and optimal performance.
- Integrated DevOps principles, including deployment, configuration management (CFengine), infrastructure inventory, and monitoring (Nagios/Cacti/Smokeping), enhancing operational efficiency.
- Optimized performance of Jboss, Voldemort, and Hadoop components, improving the responsiveness and scalability of the adserver platform.
- Participated in platform development, contributing to the design and implementation of new features and system enhancements.
### Unix Server Support Analyst | EPAM Systems
http://www.epam.com
Supported corporate Unix infrastructure for a global investment banking client, ensuring high availability and adherence to ITIL standards.
- Provided 24/7 support for corporate Unix infrastructure, including RHEL 3/4/5 and Solaris 8/10, maintaining critical system uptime for Barclays Capital.
- Managed EMC/Symmetrix SAN storage and Veritas Cluster software, ensuring robust data management and high availability solutions.
- Adhered to ITIL3.0-based processes for incident, problem, change, and capacity management, improving service delivery and operational consistency.
- Collaborated with global business and IT teams to provide seamless support in a multinational environment.
### System Administrator (Part-time/Freelance) | InSat GmbH / hi-stream.ru
http://www.hi-stream.ru
Managed Linux/FreeBSD systems and satellite ISP infrastructure, ensuring robust monitoring, backups, and user support.
- Administered Linux/FreeBSD systems for a satellite ISP startup, ensuring stable operation of critical services.
- Implemented and maintained monitoring solutions (Nagios, Cacti) and backup systems (Bacula), enhancing system reliability and data protection.
- Provided technical helpdesk support, resolving user issues efficiently and maintaining high service levels.
- Gained hands-on experience with satellite equipment and technology, contributing to specialized network operations.
### Unix System Administrator | Information-analytics center "LIGA"
http://www.liga.net
Administered complex Unix/Linux environments, virtual infrastructure, and a diverse stack of applications and databases for a legal services and news agency.
- Managed Linux/FreeBSD/Solaris administration, including connectivity with Windows and Lotus Domino services, ensuring seamless integration across diverse platforms.
- Organized and administered enterprise virtual infrastructure using VMWare and Veeam products, enhancing resource utilization and system resilience.
- Administered frontend (Nginx, Squid) and backend (Apache Tomcat, Jetspeed, 1C Bitrix, mod_perl) stacks, optimizing highload performance for web applications.
- Administered and tuned OpenX banner system on a 12-node cluster, significantly improving ad delivery performance.
- Developed and supported a remote software update system and an Internet payment platform (Perl/Apache/Nginx), improving operational efficiency and user experience.
- Managed database administration for MySQL (multi-master, multi-slave, ~250 GB), DB2, MSSQL (~100 GB), and PostgreSQL, ensuring data integrity and performance.
- Administered enterprise Java applications (Apache Tomcat) and Atlassian Jira/Confluence, alongside FibreChannel SAN (Sun Storagetek) and comprehensive monitoring (Nagios, Cacti, Veeam).
- Implemented backup planning and support with Bacula and EMC Retrospect, ensuring robust disaster recovery capabilities.
### Chief Technical Officer | SpaceGate ISP
http://www.sputnik.sg
Progressed from Technical Helpdesk to CTO, overseeing system administration, satellite technology, and technical negotiations for an ISP.
- Advanced from Technical Helpdesk Engineer to Chief Technical Officer, demonstrating significant leadership and technical progression within the organization.
- Led the system administration of high-loaded Linux servers, optimizing performance and ensuring high availability for ISP services.
- Managed satellite equipment and technology, contributing to the core infrastructure and service delivery of the ISP.
- Conducted technical negotiations, securing partnerships and resources vital for business growth and operational expansion.
### System Administrator | NTK Display ISP
http://www.evpatoria.com
Administered Linux/FreeBSD/Solaris systems and developed billing solutions for an ISP, supporting LAN/WAN and MetroWLAN infrastructure.
- Administered Linux/FreeBSD/Solaris systems, ensuring reliable operation of ISP services for a growing user base.
- Developed and implemented LAN/WAN/Dialup ISP Billing system using Perl and C, streamlining customer invoicing and service management.
- Provided comprehensive technical helpdesk support, resolving connectivity and system issues for customers.
- Managed LAN/WAN and MetroWLAN infrastructure, contributing to network expansion and service delivery.

## Education
### National Aerospace University "KhAI" | Electronic Engineering
http://www.khai.edu
- Optimization, backup and recovery of MySQL
- Nginx - Configuration and Highload
- VMware vSphere: Fast Track
- MySQL Scaling & Optimization
- InnoDB and ExtraDB
- Functional Programming Principles in Scala
- Introduction to Data Science
- Malicious Software and its Underground Economy

## Languages
- English
- Dutch
- Russian
- Ukrainian

## Certificates
### HashiCorp Certified: Terraform Associate
HashiCorp | 2024-05-01

## Skills
### Cloud & DevOps
- AWS
- EKS
- Kubernetes
- Terraform
- FinOps
- Openstack
- Packer
- Saltstack
- Nomad
- Consul
- CFengine
- Puppet
- Capistrano
- ITIL
### Monitoring & Observability
- Mimir
- Loki
- Grafana
- Prometheus
- Thanos
- Graphite
- Go-graphite
- Metrictank
- Nagios
- Cacti
- Smokeping
- Munin
- Veeam Monitoring
- IronDB
### Databases
- MySQL
- PostgreSQL
- Cassandra
- ScyllaDB
- CockroachDB
- Riak
- DB2
- MSSQL
- Project Voldemort
- Timeseries Databases
- Database Internals
### Programming & Scripting
- Golang (Go)
- Python
- Perl
- Lua
- C
- PHP
- XML
- SOAP
- REST
- mod_perl
- Bash Scripting
### Operating Systems
- Linux (Ubuntu, Debian, CentOS, RHEL, Gentoo)
- FreeBSD
- Solaris (8, 10)
- Windows Server (2003/2008)
- HP-UX
### Networking & Infrastructure
- Citrix Netscaler
- Nginx
- Squid
- Varnish
- OpenLDAP
- ActiveMQ
- LAN/WAN
- MetroWLAN
### Virtualization
- VMware ESX/vSphere
- Veeam Products
### Big Data & Data Science
- Hadoop
- Elasticsearch
- Information Retrieval
- Search
- Data Science
### Security
- Security
- Cryptography
- Privacy
### Other Tools & Technologies
- Jboss AS
- dotCMS
- 1C Bitrix
- OpenX
- Gerrit
- Git
- Bacula
- EMC Retrospect
- Symantec BackupExec
- Kayako
- DVB Hardware
- FibreChannel SAN (Sun Storagetek)

## Interests
### Hobbies
- Computer games
- Fiction books
- Emulation/old hardware
### Open Source
- Graphite Co-Maintainer
- Go-graphite Co-Maintainer
- DevOps-related Open-source projects

## Source
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