Flux logo

Mid-Level Backend Engineer

full-time Flux London

No. More. Paper. Receipts!

Were building the worlds first API to tell you exactly what youve bought, not just how much youve spent. We are looking for a talented developer with a passion for APIs and microservices who is excited at the opportunity to be involved with everything between feature planning, implementation, testing and architecture of a best in class system.

The Projects

  • Build out Blueberry, Fluxs merchant dashboard which processes complex analytics over large data sets in real time. This involves development of a GraphQL service that serves these stats and other data over websockets
  • Matching Algorithm, find an implement improvements to our matching algorithm that will allow throughput of millions of transactions per day
  • New product development (e.g. displaying nutritional info via receipts, building a better returns process for retailers or improving our developer experience)
  • Retailer and bank API integrations

The Tech Stack
Our tech stack follows open standards and handles a large volume of transactional data from some of the biggest retailers and banks in the UK. These are processed in microservices. Our backend is written in Kotlin which is based on the JVM and our frontend is primarily in React. We use GraphQL and subscriptions to facilitate real time communication between the frontend and backend and deliver analytics to our retailers in retailers. The infrastructure is built using Docker and Kubernetes.

Backend Stack

  • Java 8+ / Kotlin
  • Dropwizard / Guice / Ktor / Kodein
  • All the usual expected libraries

Wider Flux Stack

  • Pragmatic use of microservices
  • Kubernetes
  • GraphQL
  • PostgreSQL
  • React / Javascript
  • AWS
  • Vault
  • Terraform


  • 1 year of professional software development experience
  • Programming experience of working with Java
  • Desire to learn Kotlin (if no previous experience of Kotlin)


  • 2 years of professional software development experience
  • Have experience of working in at least one startup environment or greenfield development in a larger corporation
  • Have architected complex systems from scratch or have lead major pieces of functional development in a major application
  • Competitive salary and equity
  • Generous holiday allowance (28 days) - we encourage everyone to use their allowance!
  • Company pension scheme
  • Weekly team lunches
  • Annual company trip
  • Work from home Fridays
  • Central London location between Shoreditch and Old Street
  • Unlimited artisan coffee
  • Fresh fruits, nuts, beers and other snacks provided
  • Latest Macbook Pro, screen and additional tech set-up required
  • Office building perks such as weekly yoga and fitness classes

published: Dec. 7, 2018

Apply for this position