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Managed Support

Legacy Application Support UK

Keep legacy systems stable, secure, and supported, without a rebuild

SLA-backed managed support for legacy .NET, SQL Server, JavaScript web apps, and mobile applications. We patch, monitor, fix, and provide compliance evidence so business-critical systems keep running while you plan the next step.

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The legacy reality

Why legacy applications need dedicated support

The technology has not stood still, but your business still depends on systems that have. These are the pressures we see most often.

Framework end-of-life and CVE backlog

.NET Framework 4.x, older Java runtimes, ageing SQL Server versions, legacy Cordova or Xamarin mobile apps, and unmaintained npm or NuGet packages accumulate known vulnerabilities faster than your team can triage them.

Original developers have moved on

The people who built it are retired, reassigned, or have left the business. Institutional knowledge left with them, and nobody on the current team wants to touch the code.

Too critical to break, too old to rebuild now

The system runs a revenue-critical workflow. A full modernisation programme is years and hundreds of thousands of pounds away, but the business still needs it running reliably next Tuesday.

Compliance evidence is falling behind

Cyber Essentials, ISO 27001, and internal audits now expect evidence of patching cadence, vulnerability response, and access reviews. On legacy systems, that evidence is hard to produce.

What's included

Everything a legacy system needs to stay healthy

Our legacy application support service covers the full operational picture, not just ticket response.

Security patching and dependency updates

We monitor your legacy stack for vulnerabilities and apply patches through tested pipelines. Whether it is .NET, Node.js, Java, or a Cordova mobile app, even end-of-life frameworks can be hardened with compensating controls and targeted upgrades.

Bug fixes and incident response

SLA-backed response and resolution targets so production issues do not become business crises. Proper root cause analysis and permanent fixes, not brittle workarounds.

Performance monitoring and optimisation

Application Insights and Azure Monitor give visibility into ageing systems. We identify slow queries, memory leaks, and scaling bottlenecks, then tune them before users notice.

Knowledge capture and runbooks

If the original developers have moved on, we reverse-engineer the system, write runbooks, and document architecture decisions. Your team is never locked out of its own technology again.

SLA tiers to match business risk

Business-hours cover through to 24/7 managed support. Response and resolution targets, escalation paths, and on-call arrangements are agreed upfront and reviewed quarterly.

Compliance and audit evidence

Monthly reports covering patch status, vulnerability remediation, access reviews, and SLA adherence. The audit trail your governance team needs for Cyber Essentials, ISO 27001, and internal reviews.
Support or modernise?

Signals that point toward support rather than modernisation

Not every legacy system is ready for a rebuild. These are the indicators that ongoing support is the right call now, with modernisation planned later.

Support now, modernise later

  • The application is stable and serves a clearly bounded function
  • Business logic is unlikely to change significantly in the next two years
  • The technology stack, while dated, still has a path to security patches
  • A full rebuild would take longer than the remaining useful life of the system
  • Budget for a modernisation programme is not available in this financial year
  • You need time to plan the right modernisation strategy without running unsupported

Signals modernisation is overdue

  • The platform cannot scale to meet current or near-future demand
  • Security patches are no longer issued by the vendor for core components
  • Business rules are changing faster than the legacy codebase can safely absorb
  • Cost of change per feature is growing quarter over quarter
  • Integration with cloud, AI, or mobile is required and currently blocked
  • Developers with the required skills can no longer be hired at a reasonable cost

If most of these apply, see our legacy application modernisation service. We can start with support and phase modernisation in.

How it works

From discovery to ongoing support

A structured engagement designed to take on an unfamiliar legacy system without disrupting the business that depends on it.

Step One 1-3 weeks

Discovery and knowledge capture

We assess the application, infrastructure, and operational context. Where the original team is still available we run knowledge transfer sessions. Where they are not, we reverse-engineer the system from the codebase and production behaviour.

You receive a written report covering:

  • Architecture and technology stack
  • Known issues, workarounds, and technical debt
  • Security posture and CVE backlog
  • Recommended SLA tier and support model
  • Fixed-price proposal for ongoing support
Step Two 2-4 weeks

Onboarding and runbooks

We set up monitoring, alerting, and access in your environment. We write runbooks for common operational tasks, agree escalation paths, and validate the CI/CD pipeline so patches can be applied safely.

By the end of onboarding, your team has a documented, supported system instead of a black box.

Step Three

Ongoing support and quarterly review

Bug fixes, security patches, monitoring, and compliance evidence delivered against agreed SLAs. You get:

Monthly reports covering support activity, system health, patch status, and SLA adherence.

Quarterly reviews where we calibrate the support tier, flag modernisation triggers, and plan any enhancement work.

A named UK team who knows your system and is available when you need them.

"Talk Think Do were very strategic and intelligent in the way that they set it up right from the beginning, allowing us to make leaps forward."

Bill Mills

CEO, Explore Learning

Go deeper

Related services and reading

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Legacy Application Modernisation

Migrate, rearchitect, or rebuild legacy systems on Azure with AI-accelerated delivery.

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Maintainability Review

Independent technical assessment of a legacy codebase before you commit to support or rebuild.

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Internal Systems Handover

Structured handover when an in-house developer leaves or a vendor disappears.

 Blog

Legacy Application Support vs Modernisation

A decision framework for choosing between supporting a legacy application and modernising it.
FAQ

Frequently asked questions

What counts as a legacy application?

There is no fixed definition, but in practice we see systems on .NET Framework 4.x, classic ASP.NET, WCF, VB6, older Java versions, on-premise SQL Server, ageing Angular or jQuery web apps, and Xamarin, Cordova, or PhoneGap mobile apps. If the original team has moved on, the framework is out of mainstream support, or the cost of change is growing each quarter, it qualifies.

Do you support software you did not build?

Yes. A large share of our managed support work is on systems built by previous vendors, in-house teams, or contractors who have since left. We run a structured discovery phase to understand the codebase, then take ownership against agreed SLAs.

How is this different from legacy application modernisation?

Legacy application support keeps the existing system running reliably, without changing its architecture. We patch, monitor, fix, and provide compliance evidence. Legacy application modernisation is the migration or rebuild programme that replaces the underlying platform. Many clients run support while they plan modernisation, then phase modernisation in over time.

What SLAs do you offer?

We offer tiered SLAs from business-hours cover with next-business-day response, through to 24/7 managed support with one-hour response on priority-one incidents. Response and resolution targets are agreed in writing and reviewed each quarter. Most clients start on a mid-tier SLA and adjust after the first quarter of real data.

Can you support end-of-life .NET Framework applications?

Yes. .NET Framework 4.8 is still in extended support on current Windows Server versions, and we regularly support applications on 4.6, 4.7, and 4.8. For earlier versions we apply compensating controls and plan a targeted upgrade path as part of the support engagement.

Do you support legacy JavaScript web apps and mobile apps?

Yes. We support ageing Angular, jQuery, Knockout, and React web apps as well as Xamarin, Cordova, PhoneGap, and Ionic mobile apps. For mobile apps we handle store submissions, SDK updates, and OS compatibility testing alongside security patching and bug fixes.

Can support bridge us into a future modernisation?

That is the most common path. Support stabilises the system and gives the business breathing room while we assess modernisation options. Because the same UK team supports and modernises, the transition is gradual. No second discovery phase, no second vendor, no second knowledge transfer.

What does legacy application support in the UK typically cost?

Cost depends on the technology stack, complexity, and SLA tier. A typical mid-size enterprise application on a legacy stack costs between £80,000 and £300,000 per year in managed support, inclusive of engineering time, tooling, and on-call. Book a consultation for a fixed-price proposal scoped to your system.

Get started

Keep your legacy systems running while you plan the next step

Book a free consultation to discuss your legacy system, current pain points, and the SLA cover you need. We will scope the engagement and provide a fixed-price proposal.

Book a free consultation

or call 01202 375647