• Johan Lajili
  • Full stack software engineer
  • Based in London, UK
  • Typescript, NodeJS, React, Rust, AI
Johan Lajili
Old Man yells at cloud
13 Years Experience

From IE6 and jQuery to Deno with web components, not to forget my main stack: React, NodeJS and Typescript, I've seen it all. I've worked in many industries as well (finance, e-learning, gambling, advertising, etc.).

I've also worked in very different company types, from small startups to giant organisations: In my current position alone I saw the tech department grow from 3 to 200+ engineers in 4 years.

Rust crab walking about
But still learning!

Despite this, I'm always learning. I've recently been working on AI (LLM) based projects, using OpenAI's APIs to develop brand new ways to interact with software.

My interest of the moment is Rust, which I find fascinatingly elegant.

But I'm also interested in learning more about Go, Elixir, Kotlin, Swift, React Native, web3 and smart contracts and more should the right opportunity come along.

London Skyline
Open for work!

Following a merger between my current employer and another company, I'm now open to new opportunities in London, including entirely non-remote roles.

If you have a permanent position available, I'm interested in Staff Engineer (my current title), Principal Engineer, Founding Engineer or Tech Lead roles. I can be open to Senior or simply "Software Engineer" for the right company.

Discover some of my recent work



(Personal project - live - NextJS - OpenAI - TypeScript)

A side project I have made from scratch, it offers an augmented Diary experience to users who can use AI to track metrics they care about (like calories or mood), and receive weekly insights from their AI coach on how to reach their goal. It offers voice recognition and is available as a progressive web app.

It uses Next 14 (App Router with server actions etc.), Typescript, MongoDB, OpenAI's GPT-4 and more, and is currently live with over 300 users.

Golf/UFC/Tennis Event Centre

(IMG Arena - live - TypeScript - React - NodeJS - GraphQL - Websockets - RxJS - Redis - AWS - K8)

The event centres are one of the flagship products of IMG Arena. I've lead their development as a full stack Tech Lead and subsequently Head of Web Applications.

They are used by sportsbooks around the world to display low-latency live data, including 3D rendering and animations, and are used by millions of users.

One of the feats of the project is to use RxJS on the backend to transform hundreds of source websockets into a single graphql subscription tree, whilst remaining performant and scalable.

Jin's bouncing wilds

(Gamesys - live - JavaScript - PixiJS - Spine - Redux)

Jin's bouncing wild is probably the most fun slot I made at Gamesys. It's still played today by thousands of players.

Its main appeal is of course the beautiful animations, and I've worked tiredlessly to give power to the artists to animate everything themselves and be able to test it without going through the development team.

It is powered by a homemade game engine using PixiJS and Redux to provide a functional and reactive approach to game development, which works particularly well for slots. It provided us with features like time travel debugging, immutability of state, automated testing etc.

They said about me:

Paul Fairless

Paul Fairless (VP of Technology at IMG Arena)

I highly recommend Johan for any technical leadership or engineering role. Johan and I worked together at IMG Arena for almost 5 years.

Johan possesses a rare combination of creativity and technical excellence. He doesn't just tackle challenges head-on – he takes a step back, analyses the problem from multiple angles, and devises solutions that are not only effective but also elegant and efficient. This ability to think outside the box has been instrumental in the success of several key projects at IMG Arena including our award-winning Event Centres.

Beyond his technical prowess, Johan is a fantastic team player. He's always willing to share his knowledge and expertise, fostering a collaborative environment where everyone can learn and grow, demonstrated by owning and running our regular show-and-tell sessions across technology.

Simon Jameson

Simon Jameson (Technical Lead at Gamesys)

His pragmatic approach to technical problem solving has given the company many new tools and processes that benefit others as much as his immediate team. He's an incredibly talented developer with a passion for what he does and would make an excellent addition to any team lucky enough to have him.

Contact me!

I'm currently looking for a new permanent role in London, UK. If you think I could be a good fit for you and your team, by all mean please contact me at: