Service / Modernisation

Replace old software in parts. Keep working meanwhile.

We map what the old system does, put tests around it, and replace it piece by piece while your team keeps using it.

Describe your project →See an example
Approach
part by part, behind tests
Old system
runs until replaced
Data
migrated and verified
Code
in your repository

01 / What you get

Six deliverables. A plan, then working parts.

System map

What the old software does, including the rules nobody wrote down.

system-map.md

Modernisation plan

Which part goes first, why, and what stays for now.

plan.md

Characterisation tests

Record today’s behaviour, to check new code against.

tests/

Replaced parts

New code for one part at a time, released behind a switch.

feature flag

Data migration

Each part’s data moved and verified.

verify-report.md

Handover

Code, documentation and runbook, in your name.

README.md

02 / How it runs

Five steps. Repeated for each part.

  1. Assess

    what it does today

  2. Prioritise

    one part first

  3. Test

    record today’s behaviour

  4. Replace

    behind a switch

  5. Retire

    the old part, once unused

03 / Example

Old and new, compared. Then a partial release.

Illustrative. Module, counts and issue number are invented.

Example · invented data

compare · invoicing
$ make compare MODULE=invoicing CASES=samplereplayed 1,250 invoices through old and new code1,248 identical2 differ: rounding on mixed VAT rates → issue #14$ make release MODULE=invoicing FLAG=10%new invoicing on for 10% of users · old path kept

04 / What to send us

  1. 01What the system does and who uses it
  2. 02What hurts: speed, cost, missing features or a vendor leaving
  3. 03What you have: source code, database, documentation
  4. 04What must not stop, and when

05 / Related

06 / FAQ

Why not rewrite it all at once?

A full rewrite delivers nothing until it is finished, and the old system’s unwritten rules get lost on the way. Replacing parts lets you use each one as soon as it works.

We have no source code. Can you still help?

Often, yes. We can work from the database, the interfaces and how people use the system. The assessment says what is possible before any build is quoted.

Do old and new run side by side?

Yes, by default. The old system keeps running, and each new part takes over only after it passes the comparison tests.

Can we start with the assessment only?

Yes. The system map and plan are yours to use with us, with another supplier or with your own team.

Describe the old system

What it does, who uses it and what hurts.

  • Fixed-scope quote — no obligation
  • Reply within 1 business day

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