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/03 Service

Legacy modernization

We replace old systems one part at a time while your business runs. Each step is small, tested, and reversible, so you never switch everything in one weekend.

/01 Problems and fixes

Where this work often fails, and how we prevent it.

  1. /01
    The problem
    A full rewrite runs for two years and stops before it replaces anything.
    What we do
    We put a routing layer in front of the old system. We move one function at a time to new code, then remove the old part.
  2. /02
    The problem
    Nobody knows every rule in the old code, so the new system misses some of them.
    What we do
    We write characterization tests that record what the old system does today. The new code must pass the same tests before it gets traffic.
  3. /03
    The problem
    The data moves in one night, and errors appear in reports weeks later.
    What we do
    We migrate data in batches and reconcile each batch against the source. Your team reviews a report of every difference and approves it.
  4. /04
    The problem
    The weekend migration fails, and the team must restore the old system under pressure.
    What we do
    We release each change behind a switch that we can reverse in minutes. The old and new paths run in parallel until their results agree.

/02 Deliverables

What this service gives you.

You receive

  • A written map of the old system, its data, and its dependencies
  • A test suite that records how the old system behaves today
  • A migration plan in small, reversible steps
  • A reconciliation report for each migrated batch of data
  • New components in production, with monitoring and runbooks
  • A plan to retire each old component

Typical work

  1. 01A web platform that replaces a desktop application
  2. 02Services that replace a monolith, one function at a time
  3. 03A migration from an on-premises database to a managed cloud database
  4. 04A system you own that replaces an expensive vendor product
  5. 05An upgrade of a framework or runtime that no longer gets security patches

/03 Ways to engage

Three engagement models.

  • /01

    Do you have a defined project?

    Project delivery

    • One senior team from the first call to launch
    • A signed definition of done for every milestone
    • Working software to review every week
    • Handover to your team, or Ongoing ownership by ours
  • /02

    Do you need more senior engineers?

    Dedicated team

    • Engineers picked for your stack and your industry
    • Daily work inside your tools and meetings
    • A monthly check on fit and results
    • Monthly changes to team size, with notice
  • /03

    Do you have a system that must not stop?

    Ongoing ownership

    • An assessment of the system before we accept it
    • A fixed monthly budget and agreed response times
    • Security patches, monitoring, and on-call coverage
    • A written report every month

/04 FAQ

Questions clients ask first.

Do you have a different question? Ask us directly

Must we stop new features during the work?

No. Your team can continue to release features while we modernize. We plan the order of work so that the two streams do not block each other.

What if no documentation exists?

That is normal. We read the code, examine the data, and interview the people who use the system. The map we write becomes your documentation.

How do you choose what to replace first?

We rank each part by business risk, rate of change, and effort. We usually start with a part that has high value and clear boundaries. An early success proves the method to everyone.

/05 Related

/ Next step

Talk to us about legacy modernization.

Send a short note about your system and your constraints. We reply within one working day.

Start a project hello@aeontechnologies.io