Nick GroenenStaff Software Engineer

With over 15 years of industry experience, I use my knowledge of software to solve business needs. My primary interests lean towards infrastructure and complex systems, but I've typically worked across the full stack and complete software delivery lifecycle throughout my career.


Staff Software EngineerCastor · Amsterdam, Netherlands
Mar 2024 - Present

I'm currently working on a greenfield project at Castor to build a Rust-based runtime/interpreter which allows for study protocols and electronic case report forms (eCRFs) to be expressed through a custom domain specific language (DSL).

  • Language design of a DSL for study protocols and eCRFs.

  • Implementation of a lexer/parser and runtime for frontend (via WebAssembly) and backend services (via gRPC) to process the DSL.

Engineering Team Lead - PlatformCastor · Amsterdam, Netherlands
Apr 2021 - Feb 2024

Since joining in early 2019, I've been building out Castor's ability to run services internally, forming the platform team that we have today. During this time I've switched back and forth between the management and IC tracks depending on the needs of the team and the organization.

  • Created in-house database tooling for a cloud migration of 45.000 on-prem MySQL databases ("schemas") into new MySQL instances on Azure with under 1 minute of unavailability per tenant (P99).

  • Brought into production a new Kubernetes-based deployment model to replace our Virtual Machine platform, providing greater ease-of-use for users at a lower cost of infrastructure spend.

  • Implemented Earthly to set up automated, reproducible builds of in-house Ubuntu software packages.

  • Fostered a team culture with a high degree of Psychological safety, placing a strong emphasis on transparency and quality documentation, a reduction of Toil through automation, and continuous learning through practices such as pre-mortems, After Action Reviews and Post-incident reviews.

  • Reduced MySQL crash recovery time from over 10 hours to under 10 minutes by working with Microsoft to identify pathological code paths in Azure MySQL Flexible Server.

Chief Information Security OfficerCastor · Amsterdam, Netherlands
Oct 2019 - Sep 2021

While I joined Castor primarily for DevOps/SRE work, I also acted as the CISO until we had grown large enough to hire somebody for this position full-time. To this day I continue to serve as a backup to our CISO, should he be unavailable.

  • Scaled security and compliance processes while growing from 40 to 100 employees across the EU and US.

  • Supported the successful recertification audit of ISO 9001, ISO 27001 and NEN 7510.

  • Coordinated response to security incidents, including investigation, remediation and communications.

  • Ensured Castor would meet the security requirements of major clients, including the World Health Organization (WHO) for their SOLIDARITY trial on COVID-19 treatments.

Site Reliability EngineerCastor · Amsterdam, Netherlands
Feb 2019 - Apr 2021

I joined Castor as the first and sole DevOps/SRE employee and helped shape the infrastructure and platform roadmap throughout their Series A investment.

  • Reduced 80% of Toil by introducing Infrastructure as Code principles using Ansible and Terraform.

  • Helped set executive strategy to move away from local managed hosting providers, standardizing on Microsoft Azure’s cloud services.

  • Launched a dedicated server offering (“Castor Private Cloud”) on Azure.

  • Performed a cross-region migration/split of Castor’s entire user database, utilizing automation to minimize downtime and provide strong operational guarantees around preventing manual errors.

  • Opened up a new EDC region in Australia (also on Azure).

Senior Developer & InfoSec officerStartMail · The Hague, Netherlands
Feb 2017 - Feb 2019

I was one of four senior developers at StartMail, a privacy-focused email service. During my two years there, our team took ownership of the entire software and infrastructure stack, taking it fully in-house after it had previously been outsourced to an external IT company.

  • Rebuilt all core infrastructure, migrating all customer data into three new datacenters.

  • Designed Infrastructure-as-Code policies with Ansible to manage StartMail's virtual machines and physical hypervisors.

  • Served as StartMail’s information security officer.


Creator and maintainerObsidian Export
Dec 2020 - Present

Written in Rust, this open source project of mine provides both a CLI and library interface to export an Obsidian vault to regular Markdown.

Core maintainerErrbot
Oct 2012 - May 2018

A chatbot that's written in Python and which continues to flourish to this date, this was my first major involvement with open source software and project management. In addition to the usual release testing, issue triage, bug fixing and community engagement, I consider these my main accomplishments:

  • Wrote chat backends for Slack, Skype, Telegram and Gitter, extended existing XMPP and IRC backends.

  • Implemented regex- and ArgParse-based command decorators to support complex bot commands with argument parsing and validation similar to that of modern CLI applications.

  • Designed the project website and wrote the majority of API and user documentation (using Sphinx).

  • Implemented Access Control Lists (ACLs) for fine-grained restrictions of available commands.


EvenementenhulpverlenerRed Cross
Sep 2019 - Present

As a volunteer for the Dutch Red Cross, I help provide first aid at various small- and large scale events throughout the Netherlands. I'm a member of the bike teams and prefer big events like Kingsday, the Dam tot Dam or TCS Amsterdam marathons.

Noodhulp TeamsRed Cross
May 2021 - Present

As a member of the the Noodhulp Teams for the districts Kennemerland and Amsterdam, I'm on-call 24x7 to assist in case of major accidents (think airplane and train crashes, terrorist attacks, etc.). In addition to being a regular team member, I'm also designated as a driver, certified to drive emergency vehicles with lights and siren.


  • Rust
  • Golang
  • Python
  • Elixir
  • Shell
  • DevOps
  • Site Reliability Engineering
  • Incident Response Management
  • CI/CI
  • Chaos Engineering
  • Kubernetes
  • Serverless
  • Docker
  • Ansible
  • Terraform
  • Puppet
  • MySQL
  • AKS
  • ArgoCD
  • Linkerd
  • Kyverno
  • Prometheus
  • Grafana
  • VictoriaMetrics
  • OpenTelemetry
  • Datadog
Public cloud
  • AWS
  • GCP
  • Azure


Matthijs VerkaaikNick is highly structured in his approach to projects, consistently ensuring that tasks are well-defined, timelines are met, and objectives align with broader team goals. His planning and attention to detail greatly contributed to the success of our projects. Beyond his organizational prowess, Nick excelled as a mentor. He readily shared his knowledge and expertise, creating an environment where team members felt supported and empowered to grow in their roles. His guidance was crucial in my professional development, and I am grateful for the insights and skills I gained under his leadership.
Varvara TzikaAs a scrum master I was really happy to have Nick at my team. He always thrives to improve himself, the team and the organisation. He was honest and rational and that helped the team as well. He was always asking the hard questions and that helped also the team to see their problems and improve. Also, Nick was always willing to help anyone needed him.


  • English · Professional
  • Dutch · Native