Den Holtsev

DevOps & Infrastructure Engineer

Building infrastructure that stays up.

I architect production infrastructure and see it through to code, rollout and on-call: Kubernetes on bare metal and Proxmox VE, DNS and web edge, AWS and the pipelines behind them, now with AI agents in the loop.

  • 8+ yrsin production infrastructure
  • Hybridbare metal, Proxmox and AWS
  • IaCevery change versioned and reviewed
  • AIagents in daily ops, with guardrails

01 · Expertise

What I'm good at

Hands-on ownership in production, from architecture to day-to-day operations and on-call.

Solution architecture

Designing systems before building them: trade-off decisions, disaster-recovery planning, migrations, design reviews and written standards, and mentoring engineers along the way.

  • System design
  • Design reviews
  • DR planning
  • Migrations
  • Mentoring

On-premise platforms

Kubernetes on bare metal and Proxmox VE: cluster builds and upgrades from versioned installer images, node changes through pipelines, load balancing, persistent storage, and VM provisioning from code.

  • RKE2
  • Kubespray
  • Proxmox VE
  • Ceph
  • MetalLB

DNS & web edge

DNS and web services that stay fast under heavy load and attacks: authoritative and recursive DNS, reverse proxies, load balancing and TLS termination, with filtering, rate limiting and high availability.

  • PowerDNS
  • dnsdist
  • DNSSEC
  • nginx
  • OpenResty
  • HAProxy

AWS & Infrastructure as Code

AWS infrastructure in Terraform (networking, load balancing, containers, managed databases, IAM), plus fleet configuration with Chef/Cinc and Puppet: reusable roles, tested changes, gradual rollouts.

  • Terraform
  • AWS
  • Chef / Cinc
  • Puppet
  • Ansible
  • Vault

Delivery & observability

One shared pipeline flow for infrastructure code (plan on pull request, apply on merge, short-lived credentials, secret scanning), plus metrics, dashboards and alerts managed as code.

  • Jenkins
  • Docker
  • Packer
  • Prometheus
  • Grafana
  • PagerDuty

AI-assisted operations

AI agents connected to metrics, logs, tickets and pipelines; repositories prepared for agents; AI review in CI. All inside guardrails, so people stay in charge of production.

  • AI agents
  • MCP
  • Agent skills
  • AI code review

02 · AI in practice

How I use AI in infrastructure work

Practical, not hype: agents work with real metrics, logs, tickets and pipelines, and every change still goes through review.

Agents on real tooling

AI coding agents connected through MCP to monitoring, logs and ticketing, so incident triage starts from real data instead of guesses.

Runbooks as agent skills

Recurring procedures turned into reusable agent skills, so routine checks and investigations follow the same documented steps every time.

Agent-ready repositories

Repositories get agent instructions with their conventions and ordered checks (lint → test → build), pre-approved safe commands and a deny-list for secrets.

AI review in CI

An AI reviewer checks every pull request alongside human reviewers and catches routine issues before a person has to.

Guardrails

  • Read-only access by default
  • Secrets kept out of agent context
  • Production changes go through review and approval

03 · Stack

Tools I use in production

Mostly open source, picked for the job rather than the hype.

Kubernetes & virtualization

  • RKE / RKE2
  • Kubespray
  • Kustomize
  • Helm
  • Proxmox VE
  • KVM
  • Ceph

DNS, web & networking

  • PowerDNS
  • dnsdist
  • Knot Resolver
  • nginx
  • OpenResty
  • HAProxy
  • keepalived
  • nftables

AWS

  • EC2 / VPC
  • ECS / ECR
  • RDS
  • Route 53
  • Global Accelerator
  • IAM
  • S3

IaC & config management

  • Terraform
  • CDKTF
  • Chef / Cinc
  • Puppet
  • Ansible
  • Packer

CI/CD & packaging

  • Jenkins
  • Bitbucket
  • GitLab CI
  • Docker
  • RPM

Observability

  • Prometheus
  • Grafana
  • OpenSearch
  • Fluentd
  • PagerDuty
  • Nagios / NRPE

AI tooling

  • AI coding agents
  • MCP servers
  • Agent skills
  • AI code review

Data, messaging & secrets

  • PostgreSQL / Patroni
  • MongoDB
  • ClickHouse
  • Redis
  • RabbitMQ
  • Vault

Languages

  • Bash
  • Python
  • Go
  • Groovy
  • Ruby
  • HCL
  • TypeScript

04 · Contact

Have a project or role in mind?

Drop me a line and tell me a bit about it. Email is the fastest way to reach me.