Legacy Application Modernisation
Stop spending 80% of your IT budget keeping old systems alive
The UK government's 2025 State of Digital Government review found departments spending up to 80% of IT budgets just keeping legacy systems running. The pattern is the same in the private sector. We modernise applications on Microsoft Azure using the right strategy for each component, whether that is replatforming, refactoring, or rebuilding entirely. AI-augmented development accelerates the process.
Why legacy systems cost more than you think
The real cost of legacy technology is not the maintenance bill. It is the opportunities you miss while your budget and team are tied up keeping old systems running.
Spiralling maintenance costs
Most enterprises spend 60-80% of their IT budget maintaining legacy systems. That budget goes to keeping the lights on, not to innovation, growth, or competitive advantage.
Security exposure
Outdated dependencies, missing patches, and unsupported frameworks create real security vulnerabilities. Legacy systems are the number one target for attackers because they are the easiest to exploit.
Talent shortage
Engineers who know your legacy stack are retiring or moving on. Recruiting for outdated technologies gets harder and more expensive every year, and the knowledge walks out the door with them.
Innovation blocked
AI, mobile, real-time analytics, and cloud-native capabilities are difficult or impossible to integrate with legacy architectures. Your technology becomes the bottleneck, not the enabler.
What legacy modernisation actually means for your organisation
Legacy modernisation is the process of taking an old, expensive, or hard-to-maintain system and making it work on a modern platform. In practice, this means moving your software from ageing servers or outdated cloud setups to managed Azure services where it costs less to run, is easier to change, and is properly secured.
Not everything needs to be rebuilt from scratch. Sometimes the right answer is a targeted move to a managed database, a containerised deployment, or a focused refactor of the parts that cause the most pain. We assess each component individually and recommend the approach that balances cost, risk, and business impact.
AI-augmented delivery means we analyse large codebases faster, generate migration code at speed, and validate functional parity more thoroughly. For our clients, this translates to shorter modernisation timelines and lower project risk.
The right approach for each component
Not every part of your legacy estate needs the same treatment. We use the 6 Rs framework to choose the right strategy for each component based on business value, technical condition, and risk.
Rehost (Lift and Shift)
Move your application to Azure VMs with minimal code changes. Fastest path to cloud, but limited modernisation benefit. Best for: stable applications that need to leave on-premises quickly.
Replatform
Migrate to managed Azure services (App Services, Azure SQL) with targeted optimisations. Moderate effort for meaningful gains in scalability, security, and operational cost.
Refactor
Restructure code to take advantage of cloud-native patterns without changing external behaviour. Break monoliths into smaller services, adopt dependency injection, and improve testability.
Rearchitect
Redesign the application with a modern architecture: microservices on AKS, event-driven patterns, API-first design. Significant effort, but unlocks full cloud-native scalability and maintainability.
Rebuild
Start from scratch with a new application that replaces the old one. Best when the legacy codebase is beyond economical repair and business requirements have changed significantly.
Replace
Retire the legacy application and adopt a commercial or custom alternative. Sometimes the right answer is not modernisation but replacement with something that better fits current needs.
Migration paths on Microsoft Azure
We use Azure's migration tools and managed services to move your applications to the right Azure services for your workload.
Azure Migrate
Containerisation to AKS
Azure App Services & Functions
Database Migration to Azure SQL
"Talk Think Do were brilliant to work with. The platform development was done at such speed that we were able to keep our sights really high, and it felt like it was never too much that we were asking."
Amandeep Sanghera
Business Development Lead, Explore Learning
Choosing the right modernisation strategy
The 6 Rs framework guides every legacy project. The right strategy depends on business value, codebase health, and timeline.
Assessment to production, with AI at every step
Our modernisation methodology combines deep technical assessment with AI-accelerated delivery. You see value incrementally, not at the end of a long waterfall.
Assessment
We assess your legacy estate: architecture, codebase, dependencies, data, integrations, and technical debt. Cursor and Claude Code help us analyse large codebases and identify risk areas quickly. You receive a detailed modernisation report with a recommended strategy, effort estimate, and risk assessment.
Strategy & Architecture
We define the target-state architecture and choose the right modernisation approach for each component. Not everything needs the same treatment: some parts are rehosted, others refactored, and some rebuilt entirely. The strategy balances business continuity with modernisation ambition.
Migration & Build
We execute the modernisation in phased sprints using AI-augmented development tools to accelerate every phase. Parallel running, feature flags, and incremental cutover reduce risk during go-live. Together they protect business continuity. You see progress every two weeks, not at the end of a six-month waterfall.
Optimisation & Support
Post-migration, we optimise performance, cost, and security. Azure Monitor and Application Insights provide visibility into your modernised estate. Our managed application support service provides ongoing maintenance, monitoring, and continuous improvement.
Your modernisation team
Our permanent, UK-based team combines legacy system experience with modern cloud-native expertise and AI-augmented development.
Solutions Architect
Designs the target-state architecture, selects the right modernisation approach for each component, and ensures the solution meets your scalability and compliance requirements.
Full-Stack Engineers
Execute the modernisation: refactoring code, building new services, migrating data, and integrating with existing systems using AI-augmented development tools.
DevOps Engineer
Sets up CI/CD pipelines, infrastructure-as-code, and monitoring for the modernised estate. Ensures repeatable, zero-downtime deployments.
Delivery Manager
Your main point of contact. Manages scope, timeline, risk, and stakeholder communication throughout the modernisation programme.
QA Analyst
Validates that modernised applications maintain functional parity and performance with regression testing, automated test suites, and user acceptance testing.
About Talk Think Do
Talk Think Do is a UK-based software consultancy founded by Matt Hammond and headquartered in Bournemouth, Dorset.
We are a Microsoft Solutions Partner with designations in Azure Infrastructure, Digital & App Innovation, and DevOps & GitHub.
We specialise in legacy application modernisation on Microsoft Azure. We move organisations from on-premises and outdated cloud deployments to modern, scalable platforms.
Our stack includes C# and .NET, Azure Kubernetes Service (AKS), and infrastructure as code (IaC) with Bicep.
AI-augmented development accelerates every phase of our modernisation work.
Cursor and Claude Code help us analyse legacy codebases. They help us identify risk areas, generate migration code, and validate functional parity faster than manual approaches allow.
Keep legacy systems supported while you plan the next step
Not every legacy system is ready for a rebuild today. Budget, timing, or risk may mean the right call now is to keep the existing platform running reliably and plan modernisation in a later financial year.
Our legacy application support service delivers SLA-backed patching, monitoring, incident response, and compliance evidence for systems you cannot replace yet. When modernisation becomes the right call, the same UK team transitions you into a modernisation programme without a second discovery phase.
See legacy application supportModernising a mission-critical government platform
Improved code quality through targeted refactoring and automated testing, enabling faster delivery of new features across the LUIS platform
Deployed new secure Azure environments to support service growth, resilience, and future policy changes
Enhanced the LUIS API to increase flexibility, security, and interoperability for a platform supporting 25 million+ livestock identification tags
Cloud-native transformation for online tutoring
Azure cloud-native solution replaced inflexible SaaS and enabled elastic scaling for after-school activity spikes
Won the UK Business Tech Transformation Through Technology award for Compass at Home
One third of clients now use online-only learning, a capability that did not exist before modernisation
Related reading
Signs Your Legacy System Is Costing You More Than You Think
Modernise, Rebuild, or Replace: A Decision Framework
Why Legacy to Cloud Migration Is Key to Your Growth
Why Modernise Legacy Systems in the Cloud?
Choosing an App Modernisation Strategy: The Benefits of Rearchitecting
3 Keys to Implementing Microsoft Azure Strategically
Frequently asked questions
How long does legacy application modernisation take?
Timelines depend on the scope and complexity of your legacy estate. A single application replatform typically takes 4-8 weeks with AI-augmented delivery. A complex enterprise modernisation programme can take 3-9 months. Our phased approach means you see value incrementally, not just at the end.
What are the risks of legacy modernisation?
The biggest risks are business disruption, data loss, and scope creep. We mitigate these with thorough assessment, phased delivery, parallel running, and automated testing. Every modernisation starts with a detailed risk assessment so there are no surprises.
Should I modernise or rebuild?
It depends on the state of the codebase, the business requirements, and the timeline. If the existing application has sound business logic but outdated infrastructure, modernisation (refactor or rearchitect) is usually more cost-effective. If the requirements have changed significantly or the codebase is beyond repair, a rebuild may be the better investment.
What does Azure migration cost?
Azure migration costs depend on the size of your estate, the modernisation approach, and the target architecture. A straightforward lift-and-shift might cost £30,000-50,000. A full rearchitect-and-modernise programme ranges from £100,000 to £500,000+. We provide detailed estimates after assessment. See our pricing guide.
Can you support a legacy application without modernising it?
Yes. Our legacy application support service keeps outdated systems stable, secure, and compliant while you plan the right modernisation approach.
We handle:
- Security patching
- Bug fixes
- Performance monitoring
- Knowledge transfer and runbooks
That work covers systems built on older frameworks and languages. Many clients start with support and move to modernisation when the timing and budget are right.
Specialist modernisation guides
Explore our other services
Custom Software Development
When the right answer is to rebuild, not modernise.
DevOps & Modernisation
Modernise your delivery alongside your applications.
Managed Application Support
Ongoing support and continuous improvement post-migration.
API & Integration Services
Integrate modernised applications with existing systems.
AI Development & Implementation
Add AI capabilities to modernised applications.
Ready to stop spending your budget on maintenance?
Start with a free legacy assessment. We will tell you what modernisation looks like for your systems, what it costs, and how long it takes.
Book a free consultationor call 01202 375647