Legacy system modernisation with controlled risk.
We assess the code, architecture, data and integration dependencies, then create a modernisation plan that addresses technical debt alongside business priorities. AI-native analysis accelerates discovery and the restoration of testability, while named architecture and business oversight protects the modernisation decision.
Initial assessment · can begin without sharing source code
When does a legacy system become a business risk?
When changes are slow and unpredictable, critical knowledge sits with one or two people, platform support is ending, defects threaten business continuity, or integrations and security requirements can no longer be managed at an acceptable cost.
Five possible decisions
The right decision follows from risk and business criticality, not from preference.
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Retain
when the system is stable and economical to operate
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Refactor
when the functionality is sound but the code is difficult to change
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Replatform
when infrastructure is the primary constraint
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Partially replace
when a small number of modules are blocking progress
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Rewrite
only when the current model is no longer sustainable
What does the assessment cover?
- business-critical processes
- code and architecture condition
- data quality and migration
- integrations and external dependencies
- security and operational risks
- testability
- cost and expected change requirements
AI-native modernisation with controlled source-code handling
Within the environment approved for the project, AI can assist with identifying code structure, dependencies, duplication and missing tests, and with preparing documentation and migration tests.
Source code may be used only under the approved data-processing and supplier terms. The decision to refactor, replatform, partially replace or rewrite is made by a named accountable professional, not a model, based on business and technical evidence.
Phased transition
Where possible, we design for parallel operation, module-by-module replacement, data reconciliation and rollback points. Release order is determined by business risk and reversibility.
Timeline and cost
We provide the modernisation timeline and cost range after assessing the code, data, integrations, risk and transition strategy.
We separate mandatory risk reduction, operational improvements and longer-term platform replacement.
Frequently asked questions about legacy systems.
Something else? Email hello@ap4.hu and we will answer directly.
Build an evidence-based case before deciding on a complete rewrite.
The assessment shows which risks require immediate action and which changes can wait.
Request a modernisation assessment
Initial assessment · can begin without sharing source code