Callum Jefferies

Software developer

Over the last 8 years I’ve built user-centric digital products and services in sectors such as healthcare, media, hospitality, music, sport and education.

I have wide-ranging experience creating digital products inside cross-discipline teams, covering agile/lean working practices, rapid prototyping, user research, automated testing/analysis, performance, accessibility, security, usability/UX, documentation, styleguide creation, analytics, DevOps, support and open source.

I’m proficient in JavaScript, Elixir, Ruby, Python, HTML/CSS, relational databases, CI/CD, Docker and Git. I have extensive experience using Phoenix, Ruby on Rails, Node.js, React/ React Native, GraphQL, PostgreSQL and cloud-based services to build production ready software.

I’m particularly interested in how user experience shapes the business/consumer relationship. Through this I’ve developed a clear sense of what it takes to make a digital product people trust and want to use.


  1. Qualdesk – 2020–present

    Software developer

  2. Made by Many – 2012–2020

    Software developer

    • Carlsberg Adapt:
      In collaboration with a team of data scientists, I helped create a service that delivered weekly insights to bar owners derived from previously unused data sources. Responsibilities included Elixir/ React /GraphQL/ Python development, design/UX, and working abroad in Lisbon to transfer the project to Carlsberg’s team.

    • Victoria and Albert Museum:
      Ruby on Rails/ JavaScript development, design/UX, business/visitor research, and skills transfer to V&A team to rebuild the main website, events calendar and shop. Working with the V&A’s content team, I designed and built tailored editorial tools.

    • UMG Composed:
      My first foray into React in 2014, I led development of an API driven single-page app for browsing and streaming classical music in the browser.

    • Bloop:
      Carried out customer/product research, technical investigation and prototyping to create a new service for diabetes sufferers.

    • Mentoring:
      Guided a junior member of the team to grow their skills and confidence in order to take on new responsibility.

  3. The House London – 2011–2012


  4. The Arts Institute at Bournemouth – 2008–2011

    BA (Hons) Visual Communication, 2:1

Open source/ personal projects