Legacy Application Migration
A UK-based legacy modernisation team for mid-market enterprises. Discovery, lift-shift-modernise paths, parallel-run cutover, and a documented extended handover, delivered by senior solution architects under ISO 27001 controls.
Free 30-minute migration assessment · UK senior architects
UK legacy estate migrations shipped
Data-integrity safeguards on every cutover
From kickoff to fixed-quote migration plan
Certified information security controls
The pattern we see
Three problems show up in every legacy application migration we run. If any of these sound familiar, your current estate is paying interest on technical debt every month.
✕
Your platform vendor announced end-of-support next year. Security patches stop. Compliance auditors stop signing off. The clock is short and replacement options are scarce.
✓
Risk-graded migration plan agreed in 2 weeks. Critical EOL systems get a costed path before your next audit.
✕
The legacy app has 14 integrations: SFTP feeds, ODBC bridges, hand-rolled adapters. No one in the team built them. Touching anything risks weeks of breakage.
✓
Discovery + dependency mapping done first. Every integration documented, tested under parallel-run, and cut over only when proven.
✕
The people who built the system retired or left. Documentation is sparse. Tribal knowledge is gone. Every change feels like slow, risky archaeology.
✓
UK senior architects rebuild the documentation as part of the migration. You inherit a system your team can read, run, and own.
Four core capabilities. One UK migration team.
Discovery and assessment, costed migration paths, parallel-run cutover and a extended co-managed handover, delivered as one accountable service by UK senior solution architects.
Risk-scored
Asset discovery, dependency mapping, integration inventory, data-flow analysis. Risk-graded migration plan with costed paths and timeline.
6Rs analysis
Right path per workload: lift-and-shift, re-platform, re-architect, or replace. Documented decision criteria, not architect preference.
Zero downtime
The source system stays live while the target is validated, with side-by-side reconciliation, dual-write review, and cutover only when proven.
extended handover
Documented runbooks, monitoring dashboards, paired engineering with your team. You inherit a system your team can read, run and own.
How we migrate legacy systems
A predictable three-phase delivery so your business keeps running through the migration, not despite it.
01
Days 1 – 4
Asset + integration + dependency discovery. Risk-graded migration plan with costed paths. Fixed quote and timeline agreed before any code is touched. Typically 2 weeks.
02
Days 5 – 10
Wave-based migration. Lift-and-shift first to prove parity, re-platform or re-architect the workloads that benefit. Parallel-run validation before every cutover.
03
Day 11 onwards
Cost optimisation, performance tuning, observability, and scalability. Documented runbooks. extended paired-engineering handover to your team.
Why Transputec
Not the cheapest migration partner. Not the largest. But the team that consistently delivers zero data loss, board-ready risk reporting, and a documented exit. 200+ UK migrations to back it up.
01
Two decades of UK legacy modernisation. Banking, public sector, charity, retail, hospitality. We have seen your stack and shipped it before.
02
The migration plan, the scope, the price and the date are agreed in week two and held. New scope becomes V2 backlog, not budget overrun.
03
AWS, Azure, GCP, OpenShift, on-prem VMware, bare metal. Java, .NET, COBOL, mainframe, Lotus, Oracle, SQL Server. We meet you on your stack.
04
Migration runbooks, architecture decision records, interface guides, and on-call rotas. You inherit a system that your team can run without us.
Trusted by UK organisations
11 dioceses, legacy data to SharePoint Online
Insurance, WebSphere migration
Publishing, Azure cloud migration
Software Development Services
Legacy application migration sits inside our wider Software Development pillar. Most clients combine modernisation with software testing for release confidence, mobile app development to extend reach, and a UX design programme to refresh the front end.
← Back to Software Development ServicesLegacy Migration FAQs
Legacy application migration is the structured retirement of older systems (mainframe, on-prem servers, end-of-life platforms, monolithic apps, custom-built tools) and their replacement with modern, supported, scalable alternatives, typically cloud-hosted, often replatformed or refactored, sometimes lift-and-shifted. The right time to start is when ANY of the following are true: vendor end-of-support is announced, security patches stop, compliance auditors flag the system, in-house knowledge of the system has left the team, or the system cannot keep up with business growth. Transputec’s migrations are delivered by UK-based senior solution architects under ISO 27001 controls. Our practice aligns with the UK Government Technology Code of Practice. For wider context on legacy cost, read our blog on whether legacy systems are the real problem for UK public sector IT.
The decision is workload-by-workload, not estate-wide. Lift-and-shift suits stable workloads with clean dependencies that just need a supported host. Re-platform suits workloads that benefit from managed services (RDS, ECS, App Service) without app-code rewrite. Re-architect suits high-traffic or strategic workloads that justify the rewrite cost with measurable performance or scale gains. Replace suits commodity workloads where a SaaS alternative is cheaper to run than to maintain. We document the decision per workload in the migration plan, with cost + risk + time per option. Read our deeper take on cloud migration in 2026: a CTO’s guide to moving workloads without disruption.
UK Legacy Application Migration pricing is typically fixed-quote on the migration plan, with bands by workload count and migration path. Small estate (1-3 apps, lift-and-shift): £28K-65K. Mid-market (5-15 apps, mixed paths, 6-9 months): £120K-380K. Enterprise (20+ apps, multi-cloud, multi-domain, 12-18 months): bespoke quote. Fixed price, fixed timeline, no day-rate top-ups. We publish a costed plan in the SoW before contract signature. See a real migration in our WebSphere migration case study for Chubb Insurance.
Parallel-run cutover with side-by-side reconciliation: the source system stays fully live while the target gets populated and validated. We dual-write or replicate from source to target, then reconcile every record on a continuous basis. Cutover only happens when reconciliation has been clean for an agreed period (typically 1-2 weeks). If reconciliation finds a gap, source stays primary and cutover slips. Result: zero-data-loss is built into every contract. See a real legacy-to-SharePoint cutover in our Diocesan Consortium legacy data migration case study.
Three options for life after migration: (1) you take full ownership, with documented runbooks, architecture decision records, integration docs and on-call rota handed over in the 90-day co-managed period; (2) you retain us on a fixed monthly support package (typically £3K-12K depending on scope); (3) you move to a co-managed support model where your team owns day-to-day and we handle escalations + quarterly reviews. See a real Azure cloud migration in our cloud migration case study for Incisive Media, and explore the wider Software Development Services pillar.
A non-destructive readiness assessment answers four questions. 1) Stay: the app meets business needs, runs on supported infrastructure, has known maintainers, no migration. 2) Wrap: expose modern APIs in front of a stable legacy core so new builds can integrate cleanly. 3) Modernise: refactor the codebase in place (language uplift, container, cloud-native components) without changing user-facing behaviour. 4) Replace: end-of-life vendor, prohibitive technical debt or a strategic shift, full rewrite to a modern stack. We deliver this assessment in 2-3 weeks with a costed roadmap before any code is touched.
Ready to retire legacy risk?
Free 30-minute migration assessment. We map your estate, your EOL risk, and a costed migration plan with a fixed timeline. No deck. No sales pitch. Just a UK senior architect and a whiteboard.