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Application Modernisation

Safeguard existing investments whilst building a path to the future.

We believe in
collaborative transformation.

As your most important applications age they become increasingly expensive to run and may begin to fail user expectations. To maintain a competitive edge, these systems will need to be architected for the future to address evolving business needs.

Our approach to application modernisation revolves around finding the most suitable and efficient pathway from legacy systems to truly modern, cloud-native applications. We believe in collaborative transformation. That means collaborative modernisation too. We understand that rebuilding from scratch is not always the right approach.

But don’t worry if you don’t have an engineering team; we can provide all the expertise and work with you as business leaders to ensure that we modernise your platform.


We've done the research.

Updating legacy applications and migrating from on-premise to a cloud environment can be daunting, particularly for businesses struggling with a lack of technical skills.

By systemically identifying and extracting services from monolithic architectures, ‘Fission’ significantly cuts the time and risks associated with transforming to a modern cloud-native architecture.

Learn more

The 4 pillars of a modern serverless application:

Serverless Microservices

fourTheorem’s founders are leaders in microservices and serverless. We have published books and papers on these subjects and we have successful deployments under our belt.

What does this mean for you?

  • Microservices means building your system from separate components that can be created and deployed independently.
  • Microservices are now an established best practice. Done right, they give you faster development timeimproved quality and vastly increased stability for your users.
  • Serverless is the future of software. You build and deploy small, manageable components without thinking about servers or infrastructure.
  • Serverless also means using managed services for things like user accounts, storage and analytics – the parts of your system that are not unique to your core business. This decreases cost significantly and gets you where you want to be much faster.

Continuous Integration & Deployment (CI/CD)

CI/CD is about automating every step in the build, test and deployment of your system. fourTheorem deliver on this practice for all our projects. Why is this an essential part of modern application development?

  • Every time you commit completed code for a new feature, that code arrives in your production system without manual intervention.
  • We avoid the risk posed by manual steps and inevitable human error.
  • Automated deployment ensure much faster delivery.
  • Test automation gives you an assurance around quality.
  • CI/CD done right ensures an end to crippling instability and constant firefighting.


The concept of DevOps means breaking down the barriers between development and operations, deployment and operations. It allows the full team to take ownership of a feature from concept to running in production. You move faster by removing the communication bottlenecks. DevOps done right means using Infrastructure as Code. What does that look like for you?

  • All of your cloud infrastructure is written in code instead of using individual, manual steps. All parts of your system, not just the software, are deployed using an automated process.
  • You have full visibility on every single change to your entire system.
  • When required, you can rebuild your entire system with the press of a button.
  • You get a system that is predictablerepeatable and testable.


We are not just about getting your system into production fast. Observability is about everything that happens afterwards. After all, that’s the most important part, when you are delivering value to your end users. Observability is the practice of ensuring you build software in a way that gives you full insight on what is happening when it runs.

  • You want to detect issues before your users do.
  • Insights from your production system allow you to constantly improve production quality and performance
  • The right metrics are easily available, giving you a deep understanding of what your users are experiencing
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How We Work

The Methodology:


  • Understand business value
  • Establish business goals
  • Document current architecture and technology


  • Safeguard existing systems of value
  • Avoid replacement for the sake of it
  • Establish technology vision
  • Define a process for side-by-side evolution of existing and new products/features


  • Select technology and tooling
  • Build a path to the future technology
  • Incremental transformation instead of a chaotic rebuild
  • Execute business and technology vision


  • Implement continuous delivery
  • Automate everything
  • Continually measure business and technology KPIs
  • Build/ measure /optimise
  • Rapid feedback loops

The Benefits

They are all about positioning you for your own future and that future is bright.

Faster to Market

fourTheorem’s expertise in modern application development allows you to take ownership of services and make updates quicker.

Reliable Applications

Fully automated continuous integration and deployment (CI/CD) lets you go way faster without the risk.

Innovation at Speed

Modular architecture reduces the risk of change in any individual service. Reduced maintenance = more time to experiment.

Reduced Costs

Pay-for-value pricing of Serverless services can dramatically reduce running and maintenance costs, as well as undifferentiated work.

AWS Advanced Tier Consulting Partner

We are AWS MAP-compliant.
With Serverless expertise.

Blog & News

The future is always changing. We'll keep you there.

Check out our latest observations and insights into where it’s all going.