Legacy software modernization services

How a modernisation engagement runs

1. 01

   Secure access

   Source code, hosting and credentials gathered and held safely.

   Output: Controlled access

2. 02

   Audit

   Code, dependencies, hosting and data reviewed.

   Output: Assessment report

3. 03

   Safety net

   Backups, monitoring and behaviour tests added.

   Output: Protected system

4. 04

   Plan

   Route and first steps agreed.

   Output: Modernisation roadmap

5. 05

   Change in steps

   Small improvements or replacements released.

   Output: Steady progress

Tests that pin down current behaviour

Old systems often have no automated tests. Before changing them, it helps to write tests that record what the system does now, given real inputs, even if that behaviour seems odd. These are sometimes called characterisation tests. They do not judge whether the behaviour is right; they show when a change alters it. That makes it possible to improve code without accidentally changing a price calculation or a report total.

Where behaviour turns out to be wrong, it can be fixed deliberately and recorded.

What an assessment report covers

Capturing knowledge

Safeguards during change

• Verified backups

  A restore tested before significant changes.

• Monitoring

  Errors and key processes watched closely.

• Small releases

  Each change small enough to undo quickly.

• Parallel comparison

  Outputs of old and new compared for real cases.

Controlled cut-overs

When a part of the system is replaced, the switch should be planned: when it happens, how long it takes, what is checked afterwards and how to go back if something is wrong. Moving a small group of users or a share of transactions first, and widening once results are confirmed, limits the impact of any surprise. Communicate the timing to users and keep support close at hand.

Dealing with security exposure

Unsupported components no longer receive security fixes, which can leave the system exposed. Where immediate replacement is not possible, measures such as restricting network access, adding stronger sign-in and isolating the system from other services reduce risk while modernisation proceeds. Record these as temporary measures with a plan to remove the underlying exposure.

When the original supplier is gone

Some legacy systems were built by a supplier who no longer exists or no longer supports them. The first step is to establish what you hold: source code, database access, hosting accounts, licences and any documentation. If source code is missing, options narrow considerably, so check contracts and archives carefully. Where only the running system exists, careful study of its behaviour and data becomes the main source of knowledge.

Securing these assets quickly reduces risk, even before modernisation is planned.

Reporting progress on old systems

Modernisation can feel invisible because much of the early work is about safety rather than features. Regular, plain-language updates on risks reduced, knowledge captured and changes released help stakeholders see progress. A short risk register, updated as items are resolved, makes this concrete and keeps attention on what matters most.

Keeping users informed

Tell users when changes will affect them, what will look different and who to contact if something seems wrong. Early reports of odd behaviour are valuable.