Legacy Application Modernization.
Modernize or migrate in staged, reversible cutovers.
Modernise or migrate a legacy system without a big-bang cutover, with an agreed downtime and rollback plan, and without losing the business logic that's in nobody's head anymore.
About Legacy Application Modernization
The riskiest legacy code is the one everyone's afraid to touch. We start there.
Legacy Application Modernization is the careful work of moving a system that's working (mostly) onto something maintainable, without breaking the parts of it that nobody remembers writing. That covers platform, framework, database and cloud migrations as well as restructuring the code itself.
We start with an audit: what runs, what it does, what depends on it, and what the risk map looks like. Then we modernise incrementally using the strangler pattern, shadow deployments and parity tests, one slice at a time, with a rollback plan for every stage.
The finished system is checked against agreed parity tests and runs on infrastructure your team wants to be on-call for, with a documented migration process you can apply to the next slice yourself.
Project deliverables
What we can deliver.
These are possible deliverables for this service. Your statement of work defines the selected scope, price, milestones, acceptance checks and responsible reviewers.
- 01Full system audit & risk register
- 02Staged migration plan with rollback per stage
- 03New services deployed alongside legacy, in shadow
- 04Parity test suite (behaviour-verified)
- 05Data migration with row-level reconciliation
- 06Progressive cutover & legacy decommission plan
Business use cases
Where Legacy Application Modernization fits.
Explore practical applications of Legacy Application Modernization and the workflows each can support. We agree the implementation scope around your users, systems and priorities.
Monolith to services
Break out the highest-risk service first, deploy in shadow, cut over when parity holds.
Cloud migration
On-prem to cloud, or one cloud to another: lift-and-optimise (not lift-and-shift), with data parity-verified.
Framework or database move
Move off an unsupported framework version or database engine with row-level validation, without freezing feature work.
Technical approach
Capabilities your project needs.
We select tools around your requirements, existing systems and operational constraints. These capabilities guide the architecture and implementation.
- Strangler pattern
- Shadow deploys
- Parity testing
- Data reconciliation
- Feature flags
- Progressive rollout
Our delivery process
From requirements to handover.
We plan requirements, architecture, design, implementation, testing, release and handover. The proposal identifies the engineering review and client acceptance points for your project.
Service questions
Legacy Application Modernization: common questions.
How do you avoid breaking things nobody documented?
The parity test suite. If the legacy has no tests, we first characterise it with behavioural tests. Every migrated behaviour then runs against the legacy and the new system in shadow, and the diff has to be zero (or explained) before cutover.
Can you work on our system while features are still shipping?
Yes, that's the point of the strangler pattern. Feature work continues on the legacy; we add the new system alongside and cut over service-by-service.
How do we move off spreadsheets or an old system without disrupting the business?
Move in stages, not in one cutover. Each stage moves one workflow or set of records, runs alongside the old system until parity tests show the same results, and has a rollback path tested before cutover. Any downtime, the cutover window and sign-off are agreed before each stage, so daily work keeps running. The plan depends on how clean and consistent the current data is, how many people and processes rely on the spreadsheets or old system, which integrations read from it, how long both can run side by side, and the reconciliation needed to prove migrated records match row by row. The rollback steps, data checks and rollback window are written down for each stage.
Related services
Services that work together.
Plan your project
Discuss your requirements.
Tell us your goals, current systems and delivery priorities. We will define the scope and provide a written quote for Legacy Application Modernization before implementation.
Timelines, ownership, third-party licences, warranty and support are agreed for your engagement.