Software that has to work.
For over twenty years MLJ Systems has built software where reliability isn't optional — furnace monitoring and optimisation for Tata Steel, cloud platforms for green hydrogen, enterprise .NET systems, mobile apps and applied AI. The environments change; the engineering standard doesn't.
Trusted with the systems behind UK steelmaking
Our optimisation, monitoring and reliability work with Tata Steel delivers measured, audited results — and we're now supporting the transition to Electric Arc Furnace steelmaking at Port Talbot, one of the UK's most significant industrial decarbonisation projects.
saved through charge balance model optimisation of raw material use.
saved per year in failure reductions through one plant reliability project.
What we do
We're a small, senior team. Every project gets experienced engineers who have designed, built and deployed production systems in demanding environments.
Plant & manufacturing systems
Monitoring, utilisation and data systems for heavy industry — built to run reliably on the plant floor, integrated with the process systems you already have.
Mathematical optimisation
Solver-driven optimisation of real industrial processes — charge balancing, scheduling, resource allocation — where a better answer is worth millions.
Enterprise software development
Modern .NET, C# and SQL Server applications with clean architecture, automated deployment and the security discipline enterprise clients expect.
Applied AI development
Practical AI that ships: intelligent document processing, LLM integration into existing systems, and AI-assisted engineering — deployed securely, with your data staying yours.
Legacy migration & integration
Deep experience moving bespoke legacy systems — including OpenVMS and long-serving WinForms estates — onto modern platforms, and integrating new software with what's already there.
Web & mobile apps
Consumer and business apps for iOS, Android and the web, backed by fast, secure APIs — built with the same engineering discipline as our industrial work.
Data & reporting
KPI frameworks, data dictionaries, warehousing and business intelligence that turn plant and business data into decisions.
Dedicated development teams
Specialist help on a bespoke project, or longer-term capacity embedded in your team. Our engineers integrate, guide and deliver.
Case studies
Three projects that show the range of what we deliver.
Years of plant monitoring and reliability work, now extended into the Electric Arc Furnace transition — modernising key plant systems, building data and KPI foundations for the new furnace operation.
We also built the optimisation behind the charge balance model, using the Gurobi solver to optimise raw material charging across the operation.
£3m a year saved through optimisation; £100k+ a year through failure reduction.
Hydrogen production management software for one of the UK's green hydrogen pioneers — built in Blazor on Azure, giving operations teams live visibility and control of production.
A modern cloud platform for an emerging clean-energy industry.
Migration of highly bespoke, decades-old OpenVMS systems onto a modern, supportable enterprise platform — preserving hard-won business logic while unlocking modern tooling, security and integration.
Critical systems moved without disrupting the operations that depend on them.
AI development, done properly
Most businesses don't need an AI strategy deck — they need working software that uses AI where it genuinely helps. We build AI features into real systems: securely deployed, integrated with your data, and measured against outcomes rather than hype.
Because we come from enterprise and industrial software, we bring the same discipline to AI: security-first architecture, private deployment options, and engineering rigour from a CISSP-qualified leadership team.
LLM integration
Adding language-model capability to your existing applications and workflows — search, drafting, summarisation, decision support.
Document & data intelligence
Extracting structure and answers from the documents, reports and records your business runs on.
AI-assisted engineering
We use AI tooling in our own delivery to move faster without cutting corners — and can help your team adopt it well.
Built in Swansea. Trusted by industry.
MLJ Systems is a software development company based in Swansea, South Wales. For over two decades we've served clients from local businesses to Tata Steel, with a track record of delivering systems that stay in production for years.
We're small by design: senior engineers, direct communication, no hand-offs to a junior bench.
We build our own products too — including Harbour, our co-parenting app — so we know first-hand what it takes to design, ship and run consumer software, not just build it for others.