christoph ender

about me

I'm a freelancer working on IT operations, networking and development. I've been doing a great variety of projects, from the development of web shops over private banking frontends up to the development of a complete clinical trial project system. Over many years, I've been using and gained experience in the following technologies:

technical experience

  • Operations
    Monitoring utilizing icinga[web]2, high availability with VRRP/keepalived, Loadbalancing using mostly Kemp Loadmaster technology, network planning and implementation scaling all the way from on-premise-LANs to entire cloud-based infrastructure utilizing OCI, Hetzner or other cloud providers.
  • Languages
    Java, PHP, JavaScript, C, Visual Basic .NET, Perl, SQL.
  • Networking
    IPv4/IPv6, Routing, OpenVPN, IPSec via StrongSwan and various hardware implementations, Wireguard, ssh, dhcp using old ISC DHCP or new ISC Kea DHCP, DNS using bind/unbound or others.
  • Mail
    Implementing full fledged high-availability IMAP-/SMTP-Servers using postfix with postscreen, dovecot with dsync-clustering, amavis, spamasassin, dkim/dmarc/spf and sieve.
  • Databases
    Oracle 11g/19c, PostgreSQL, MySQL/MariaDB, InfluxDB
  • Markup Languages
    HTML, XML, CSS, XSLT, XSL-FO, XSD, SVG, Markdown
  • Technologies
    OpenID, OpenAuth, Apache, CalDAV- and CardDAV-servers using DAViCal, Ant, Apache Tomcat, Servlets, JDBC, JUnit, Cocoon, JMX, RMI, FOP, btrfs, zfs, LUKS, nfs, radvd, Docker/Containers, jQuery, TeX/LaTeX, Samba, EWS, Bitwarden, GnuPG, Node.js.
  • Shells
    bash, Powershell, zsh
  • Version control
    git, svn, cvs
  • Basic knowledge
    C++, C#, M4, cmake, nginx, Informix, MQTT, nroff/troff

professional experience

  • terminland
    Terminland is the leading provider for online-scheduling systems in Germany. I'm supporting them by working on database, network and loadbalancing operations as well as in development.
  • pegasus spiele
    Pegasus Spiele is a german game publishing and distribution company where I've been working on online shop functionality and IT operational management, from backup systems over Postfix-based newsletter systems to ecommerce-related data synchronization since 2000.
  • easyclin
    Over several years from 1999 to 2013 I've implemented a validated clincal trial management system for Synapcon Ltd. along with the entire IT operational management, from Postfix-based company mail server to a fail-safe server environment in two separate data centers.
  • tu darmstadt and deutsche telekom
    I've been doing research for the foundations of a recommendation system for TU Darmstadt and Deutsche Telekom AG in 2009.
  • dresdner bank
    In 2002 and 2003, as well as from 2005 to 2006 I've been supporting the Dresdner Bank AG – now Commerzbank AG – in the implementation of a private banking frontend.
  • fizmo
    fizmo is an interpreter for Z-Machine programs. This virtual machine is able to run old, text-based games, as well as modern interactive fiction.
    I'm interested in typography, fonts, layout and things related, resulting in a typeset version of the Sherlock Holmes canon at