Legacy Modernization

Legacy modernization that keeps the business running.

Your system still carries the business, but every change gets slower and riskier. We assess what you have, choose the parts worth replacing and move them one slice at a time, with data migration and rollback planned before anything switches.

Scope your modernization →

DIRECT ANSWER

Legacy modernization changes the architecture, runtime or platform of a system you already own and operate, in stages, while it keeps serving users. The engagement covers an assessment, an agreed sequence of replacements or upgrades, data migration and verified cutovers.

Best for

Owners of a working system whose framework, runtime or architecture now blocks change
Teams that need a staged plan instead of a big-bang rewrite

Consider another approach

A change of provider that first needs access recovery and knowledge transfer
COBOL, mainframe, SAP customisations or niche embedded firmware

Modernize your own system, not someone else’s handover

This page is for a system you already own and run, built by your team or by a provider you still work with. If the previous provider is gone and nobody holds the access or the knowledge, start with Software Takeover; its legacy assessment and the bounded dependency upgrade stay there with their existing terms. Moving servers or cloud accounts without changing the application belongs to Cloud Migration. Routine updates and fixes on a stable system are Software Maintenance.

Choose the change from what you find

Age alone does not justify a rewrite. The assessment compares options per component: cost, risk, and what the business keeps doing while the change happens.

Incremental replacement

Route one capability at a time to a new implementation behind a stable interface (the strangler pattern). The old path stays available until the new one has proven itself.

Framework and runtime upgrades

Move to supported versions of the language, framework and libraries. Large version jumps become a sequence of smaller, tested steps.

Re-platforming

Move the application to a different runtime or hosting model with minimal code change, for example into containers. A pure infrastructure move is scoped as a cloud migration.

Data migration

Map old and new schemas, transform and reconcile records, and rehearse the migration on a copy before the real run.

Keep the business running while parts change

Start with the slice that has the highest blocking cost and the lowest coupling. Each slice needs the behavior that must stay identical, tests or recorded reference outputs that check it, a switch (feature flag, routing rule or release), a rollback path and a named person who approves the cutover. An earlier application version may not undo database or external-system changes, so data steps are planned separately from code steps. Platform fit is confirmed in the assessment.

Illustrative acceptance: old and new path return the same result

For an agreed capability, a recorded set of realistic, non-sensitive requests runs against the old and the new implementation. Every difference is listed, then explained or fixed. A data-migration rehearsal on a copy records row counts, checksums for selected fields, rejected records and duration. The cutover then runs with a rehearsed rollback. This illustrates an acceptance exercise, not a customer result or a guarantee that every edge case is covered.

Assess, deliver in slices, hand over

Scope and quote each phase before work starts. You can use the assessment with your own team or commission the agreed slices.

Assessment
Receive a component map, a version and dependency inventory, confirmed risks and a staged plan with options per component.
Staged delivery
Each slice is quoted before work starts, as a signed fixed scope or within a monthly retainer, and released with its checks and rollback.
Handover
Receive updated documentation, runbooks, removed old code paths and a clear list of what your team now operates.

Bring access, the critical workflows and the people who know the rules

We need repository and infrastructure access, the business-critical workflows, known incidents, the current version list, data volumes and the people who know why the system behaves the way it does. Read access and production changes are separate permissions. For background, read how we approach architecture remediation without a rewrite and a worked upgrade or migrate decision for legacy PHP.

// proof

Modernization in existing engineering work

Hyperstate AI documents splitting a GPU-heavy monolith into separate services and moving manual deploys to containerized, orchestrated infrastructure while the product surface stayed the same. Polity documents a frontend and tooling stack migration and the consolidation of legacy CI across services while features kept shipping. MyMerch shows the opposite call: a working system improved in targeted places without a rewrite. None of these cases is a mainframe or ERP replacement, and none promises the same outcome for another system.

GPU Monolith → Microservices

Split a GPU-heavy monolith into orchestrated services and swapped self-hosted ML libs for scalable alternatives. Latency and cost …

Python Django OpenAI API

7 services Unified Testing

1.5 years owning QA across seven services and multiple vendors. Quality stayed shippable through every refactor.

React Java/Kotlin Go

~50% Efficiency improvement for the MyMerch team

MyMerch’s team puts the efficiency gain at ~50%. Fewer delivery errors, improved Shopify conversion, no rewrite.

Shopify Shopify Liquid JavaScript

These are selected projects, not our full portfolio. We have shipped 100+ products since 2018.

Questions before you start

Do we have to rewrite the whole system?

Usually not. Most systems have parts worth keeping. The assessment shows which components to upgrade, which to replace and which to leave alone, and a full rewrite is only recommended when the numbers support it.

How is this different from a software takeover?

A takeover moves responsibility from one provider to another: access, documentation and release safety come first. Modernization changes the shape of a system you already control. If you need both, the takeover comes first, because you cannot safely change what nobody can build and release.

Can the system keep running during modernization?

That is the default plan. Each slice switches with a rollback path. If a data step needs a maintenance window, it is agreed in advance with the people affected.

Which stacks do you modernize?

Web, mobile and cloud-native systems, typically PHP, Python, Node.js and .NET backends with web or mobile frontends. Specific platform fit is confirmed in the assessment. COBOL, mainframe, SAP customisations and niche embedded firmware are not our craft.

What does modernization cost?

The assessment is a fixed scope, priced after a short intro call. Each slice is quoted from what the assessment finds. A number given before anyone has read the code is a guess.

Scope your modernization

Describe the system, its stack and what blocks change today. A short, non-sensitive outline is enough for the first conversation.