Experienced in systems architecture, scaling large rails web applications, devops and managing remote lean teams.

Has more than 20 years of software engineering experience.

Personal Details

  • Mobile: +61449793553
  • Email: simon@rentzke.com
  • @sren
  • github
  • goodreads
  • stack overflow
  • kiva
  • Skills

    Ruby and Rails – I have been using Ruby since 2006. I have a good knowledge of the Rails framework and have extensive experience with many of the popular Ruby gems.

    Databases – I have been using Postgresql and MySQL for over 10 years. I am also a confident user of Redis, ElasticSearch, Google's BigQuery and Amazon's Redshift. I also have some experience using document oriented databases such as DynamoDB, MongoDB and CouchDB.

    Devops - I am a confident user of AWS and Google Cloud Services, and take an active interest in Docker, as well as Kubernetes.

    Javascript - I have been using Javascript for a number of years, and although not an expert, I have a working knowledge with Node.js, and some front end frameworks such as React, Vue.js, AngularJS and Backbone.

    HTML & CSS – I have helped with the UI on a number of projects and am confident with HTML and CSS.

    Kanban & Scrum – I have worked both individually and in teams ranging in size from 2-20 people. I have a proficient understanding of the Agile process (specifically using Scrum) and am comfortable applying it to projects I work on.

    Operating Systems – I am comfortable with Linux-based servers. I primarily use Mac OS X as my development OS but also have experience with Ubuntu.

    SCMs – I have been using Git for a number of years and am a confident user.


    Language/Tech Interests: - Grpc, Google PubSub, Lambda, Heroku, Go (Golang), Python, Rust, GraphQL, AWS Sagemaker, Tensorflow

    Growth & Strategy - I have been on many leadership teams and have taken a keen interest in the strategic goals and growth decisions of the organization.

    Business Development - Experienced with estimations, contract negotiation, client relationships.

    Marketing/Sales - Helped with the marketing and sales strategy.

    Finance - I have experience managing cash flow and and keeping the accounts in order.

    Recruitment - I have interviewed over 100 people, and helped build great development teams.


    Finance, lean teams, sustainability, machine learning, economics, renewable energy.

    Latest Experience

    Software Engineer, NewRetirement (2021 - Current)

    Part of a small team helping scale up an application that helps users look after their finanical wellbeing and ensure they have a safe path into the future.

    VP Engineering, Intellum (Nov 2017 - 2021)

    Part of a brilliant team that built a customer education platform that tens of million of people used to improve their knowledge.

    I was responsible for building the engineering team, scaling the application with Ruby, Postgresql, ElasticSearch, AWS and GCS. I supported large enterprise clients such as Google, Facebook and Amazon.

    Also responsible for helping engineers reach their potential, and setting code guidelines and development processes.

    Principal Software Engineer, Intellum (Nov 2011 - Nov 2017)

    Worked predominantly on Intellum's flagship product Exceed to deliver one of the best learning platforms in the world.

    Team Lead, NetEngine (Jan 2011 - Nov 2011)

    Tightened up the development process of key projects. Introduced continuous integration and a healthy test driven ethos. Managed clients expectations and delivered weekly deploys. Balanced clients urgent requirements for 4 key projects with limited resources.

    Software Engineer, Unboxed Consulting (Oct 2006 - Jan 2011)

    Primary role as a contract software engineer. Worked in many startups to improve agile processes building quality products using Ruby on Rails. Was also involved with financial administration, client relations, recruitment and marketing.


    University of Cape Town, Bachelor of Business Science - Information Systems (January 2002 - November 2005)

    Information Systems, Business Strategy, Project Management, Operations Management, Microeconomics, Macroeconomics, Financial Mathematics, Statistics, Accounting, Finance, Business Law, Marketing.