Senior API Engineer (C#)


Accelerate your career and learning by being one of the first 10 employees at the next fast growing Fintech Startup.

Upside is looking for a developer whose existing skills, experience and knowledge will complement and support our growing team. You’ll be engineer #3 which means company options as well as autonomy, and getting to work with a start-up which in its first year won 4 industry awards and is one of 2021’s hottest fintech startups.

Although we’re a small team now, the sky's the limit, and our ambitions are big. In the next 12 months alone, we expect to grow a dev team of ~15 people which you’ll have a leading role in setting the culture and standards for.

About Upside

Upside is on a mission to help ordinary people save. More than 11m people in the UK have less than £100 in savings. Round-up and habit-changing apps want to use money that people don’t have to build savings. Instead, we find the money in peoples' data and release it to them as upside (cash), giving them extra money to save. At the same time, we help our partners in the retail sector provide truly personalised offers helping them to generate more loyal customers as well as attracting new customers - ultimately helping them to grow, by creating a virtuous cycle that benefits everyone.

Customers simply connect their bank accounts via open banking, spend at retail partners on their normal debit and credit cards, and earn rewards immediately.

As a D2C app we are already gaining great traction*. Our ultimate goal is to build a platform for banks and other service providers looking for a rewards solution that customers love, allowing us to help more people to save in the UK and ultimately all over the world. We have multiple distributors in our development pipeline already, and more on the way.

* If you are on iOS, you can try it yourself. Android is coming soon!

About the role

You’ll work directly with the founders as part of a tight-knit product team to translate ideas into impact as fast as possible. You’ll develop step-change experiences from scratch which directly help to put more money into peoples’ bank accounts instead of Facebook, Google Ads and Data resellers’ pockets.

We are looking for Senior C# Engineers to help build our public API. This API will ultimately be the very core of our platform. You'll have a strong opportunity to influence and lay the foundations of this API, which we expect to be based on a streaming micro-services based architecture.

As a senior engineer at Upside, you'll have the opportunity to play a leading role, helping to define how we work, the design patterns we use, the standards we meet. You'll mentor and support more junior engineers as we grow, helping to make Upside a great place to work, learn new things and build something amazing.

Why engineering @ Upside

You'll be joining a small team that values code quality and takes pride in delivering great results for both our customers and the Upside business as a whole.

We believe in collaboration, learning from and supporting one another as we work. We strive for high engineering standards and use modern tools and techniques to achieve them. You'll be working in an environment where we practice DevOps, Continuous Delivery, and Test Driven Development.

Upside is a data company first and foremost, and we will be dealing with data at serious scale. Using this data to unlock savings for our customers is an exciting problem to solve, providing fertile ground for learning, experimenting and growing individually and as a team.


As a senior engineer, you will be responsible for:

  • Hands-on development of key components of the Upside platform, primarily focussed on delivery of our Public APIs, leveraging Upside's existing technology stack based on AWS and C#.NET Core.

  • Helping to define our software architecture going forward.

  • Setting best practices and helping and mentoring other developers to write the best code of their careers

  • Reviewing code from other engineers (including our CTO!)

  • Helping to drive recruitment and grow our teams, including acting as line manager and mentor to small teams

You will operate as part of a small team, and will therefore be willing and able to work independently, and make and execute on outcome focussed decisions where appropriate. You’ll build close bonds with other team members and work together to achieve the best results for our customers and business.

The ideal candidate

  • You will have strong software architecture and engineering skills, backed up with experience and battle scars from previous projects

  • You’ll be a good communicator, and you’ll enjoy working in mixed teams of business and technical people.

  • You’ll embrace the opportunity to learn new technologies, programming languages, tools and techniques.

  • You’ll like teaching and mentoring others as much as learning yourself.

  • You will relish the prospect of growing with the company, and learning how to scale code, teams, and businesses

  • You may or may not have a degree in computer science, but you have a good working knowledge of computer science fundamentals


  • You will have experience in FinTech or MarTech environments, or a background in large scale data processing and streaming environments

What we are offering in return

Upside is an early stage startup. In return for working at Upside, you will receive:

  • A competitive package, comprising a salary between £45-60k AND Stock Options depending on your experience and skills. Salary will be regularly reviewed as we go through future investment rounds.

  • An opportunity to get in at the ground floor of a company which is growing fast.

An opportunity to build a fantastic product which customers love, in a challenging but supportive environment.

Apply Now

Upside Money Limited. 
A company registered in England and Wales
(Company No: 12393337) whose registered office is at 

71-75 Shelton Street, London, 

All Rights Reserved 2020 ©

Upside Money Limited. 
 A company registered in England and Wales
(Company No: 12393337) whose registered office is at 

71-75 Shelton Street, London, 

All Rights Reserved 2020 ©

Join our Team

Paul Russell   CTO

Location: UK, Remote