Legacy System Modernisation in the UK

Refactoring improves code structure and performance within the existing architecture. A full rewrite replaces the old system entirely with new code, typically when refactoring is too costly or the technology gap is too wide. Most modernisation projects combine both: refactor critical business logic, rewrite UI layers, and migrate data incrementally. This hybrid approach reduces risk and keeps teams delivering features during the transition.

Data integrity is critical. We use staged migration strategies: run old and new systems in parallel, validate data sync between them, test rollback procedures, and build reconciliation checks. Schema mappings are tested repeatedly before cutover. If issues arise, we revert to the old system without data loss. This parallel-run period adds time but eliminates the risk of unrecoverable data corruption.

Yes. Gradual migration is often safer than a single cutover event. Techniques include feature flags to route traffic between old and new systems, API gateways to decouple front-end from back-end changes, and strangler fig patterns to incrementally replace components. You scale up new services slowly while retiring old ones piece by piece. This extends the timeline but reduces operational risk and gives teams confidence before going fully live.

We assess what truly depends on that infrastructure versus what is just historical convention. Often, old hardware constraints are no longer relevant in the cloud. If dependencies are genuine, we either emulate them (containerised old environments) or refactor that layer separately. The goal is to move core business logic to modern platforms while minimising changes to proprietary or heavily customised systems.

Timelines depend on codebase size, system complexity, data volume, and your tolerance for parallel running. Small modernisations may take 3-4 months. Large monolith-to-microservices projects typically run 9-18 months. We scope each project individually, breaking it into milestones so you see progress and can adjust scope without delaying the entire delivery. Regular demos and retro-active reviews keep the project on track.

Our developers specialise in extracting business logic from legacy code, designing cloud-native architectures, leading data migrations, and managing infrastructure as code. We also bring ops expertise to containerisation, Kubernetes, CI/CD pipeline design, and monitoring. Equally important is our consultative approach: we listen to your IT strategy before prescribing a technical solution, so modernisation aligns with your broader business and technology roadmap.