CORE Re-engineer · Legacy application modernization
Rebuild the system nobody wants to touch, with every rule it carries.
The business logic is right. The technology or the architecture underneath it is not. Re-engineer recovers every rule from the existing code first, then rewrites or re-architects around it, and proves the new system behaves exactly like the old one.
Two kinds of rebuild
Change the stack, change the shape, or both.
Rewrite
Move to a modern technology stack
The language, framework or platform has outlived its usefulness: nobody can hire for it, it will not pass a security review, or it only runs in a browser that no longer exists. CORE moves it onto a modern stack with the same behavior.
Re-architect
Change how the system is built
The code works but the architecture holds you back. It cannot scale, cannot move to the cloud, cannot serve several tenants or meet new security requirements. CORE reshapes the foundations and leaves the logic exactly as it was.
Rewrites and re-architectures
See how CORE rebuilds, pattern by pattern.
Three rewrites CORE has delivered and the six re-architectures most modernization projects fall into. Each one starts by recovering the business rules and ends by proving parity.
Self-heal. When a parity test shows the new code answering differently, CORE traces the difference to the rule and corrects it before review.
What you get
- A catalog of the business rules, approved by your team
- Clean services in your repository
- Parity evidence your auditors can follow
Rewrite: ASP backend
Fifteen years of rules, recovered before anything is rebuilt.
A loan-origination backend written in classic ASP, undocumented, with the original developers long gone. CORE indexed the code, extracted the business rules, and generated clean services with tests, verified stage by stage by senior architects.
What CORE does
- Indexes the whole legacy codebase
- Extracts every rule, calculation and edge case
- Presents rules in plain language for your experts to confirm
- Generates services on a modern stack
- Adds unit and integration tests for every rule
Self-heal. Layout and behavior differences between browsers are found by testing and fixed automatically before handover.
What you get
- The portal working in Chrome, Edge, Safari and Firefox
- Identical workflows for your users
- A report of every dependency replaced
Rewrite: IE-only intranet
Free a business-critical portal from a browser that no longer exists.
An intranet portal that only ran on Internet Explorer blocked a company-wide browser move. CORE found every browser-locked dependency and replaced each with a standards-based equivalent, keeping every workflow the same.
What CORE does
- Finds ActiveX, JScript, VBScript and IE-only CSS
- Replaces each with a standards-based equivalent
- Keeps screens and workflows exactly as users know them
- Tests every journey in all modern browsers
- Removes plugin and compatibility-mode dependencies
Self-heal. Mismatches from the side-by-side run are traced and fixed automatically, then the comparison continues.
What you get
- C# services your Microsoft-stack team can own
- Side-by-side parity results
- A documented cut-over and rollback plan
Rewrite: Java EJB to .NET
Consolidate on one stack without losing two decades of logic.
After an acquisition the business standardized on Microsoft tools. CORE extracted the Java system’s rules, generated equivalent C# services with equivalence tests, ran both side by side to prove parity, then cut over with a rollback plan ready.
What CORE does
- Maps EJB components to service boundaries
- Extracts rules and data access patterns
- Generates C# services and tests
- Runs old and new side by side on the same inputs
- Plans a cut-over with rollback
Self-heal. Configuration drift and failed health checks after deployment are corrected and re-verified automatically.
What you get
- A target cloud architecture, approved first
- Terraform for your environment
- A migration and rollback runbook
Cloud migration
Move to AWS, Azure or Google Cloud with every dependency accounted for.
CORE maps every host, storage, network and service dependency, chooses lift-and-shift or cloud-native per component with you, and delivers the migrated system with infrastructure as code.
What CORE does
- Maps hosts, storage, networks and service calls
- Recommends an approach per component
- Generates infrastructure as code for your account
- Migrates configuration and secrets safely
- Tests the system in the cloud before cut-over
Self-heal. Contract mismatches between services found in testing are fixed and re-tested automatically.
What you get
- Independently deployable services
- Contracts and documentation for each
- Equivalence tests across the whole system
Monolith to microservices
Split along the lines the code already suggests.
CORE finds natural service boundaries from data access patterns and call graphs, proposes the target design for your approval, and delivers services with clear contracts and event streams where they fit.
What CORE does
- Analyzes call graphs and data ownership
- Proposes service boundaries for approval
- Defines contracts between services
- Separates data per service safely
- Introduces events where synchronous calls do not fit
Self-heal. Rows or values that fail the equivalence check are traced to the transformation and corrected automatically.
What you get
- A migrated, tested database
- Equivalence evidence for every table
- Repeatable scripts for rehearsals
Database modernization
Leave Oracle, DB2 or SQL Server and prove nothing was lost.
CORE translates the schema, writes the migration scripts, updates the data access layer and proves data equivalence between the old and new databases, table by table.
What CORE does
- Translates schema, procedures and types
- Writes repeatable migration scripts
- Updates queries and the data access layer
- Compares row counts and checksums
- Plans the cut-over window with you
Self-heal. Any query that leaks across tenants in testing is fixed and the isolation suite re-runs.
What you get
- A multi-tenant platform
- Isolation tests you can re-run anytime
- Tenant admin and onboarding
Multi-tenant platform
One platform, many customers, no data crossing between them.
CORE finds every point where tenant data must be separated, adds row-level security or schema-per-tenant isolation, and delivers onboarding and admin tools for running the platform.
What CORE does
- Finds every query and file path that touches data
- Adds isolation at the database and application layers
- Updates sign-in and permissions per tenant
- Adds tenant onboarding and admin tools
- Tests that no tenant can see another’s data
Self-heal. Gaps found by a CORE compliance review are fixed in the same run and the review re-scores automatically.
What you get
- The upgraded application
- A control-by-control evidence pack
- A remediation report for your security team
Security posture upgrade
Add the controls the app was built without.
A system that works but cannot pass a security review: no single sign-on, weak logs, plain-text personal data. CORE adds the missing controls against your target framework and delivers evidence for your auditors.
What CORE does
- Assesses gaps against SOC 2, ISO 27001, HIPAA or PCI DSS
- Adds single sign-on and role-based access
- Encrypts personal data at rest
- Adds audit logging and secret management
- Produces evidence tooling for auditors
Self-heal. Messages that fail in testing are traced, the consumer is fixed, and the flow is re-run end to end.
What you get
- Faster responses for users
- A resilient event-driven design
- Monitoring for queues and failures
Event-driven refactor
Stop making users wait for work they do not need to watch.
Long chains of synchronous calls and nightly batch jobs slow everything down. CORE identifies which flows should be asynchronous, introduces event streams, and builds in retries and dead-letter handling.
What CORE does
- Finds slow synchronous chains and batch jobs
- Designs events and consumers for approval
- Introduces Kafka, RabbitMQ or cloud-native queues
- Adds retries, idempotency and dead-letter handling
- Proves the same outcomes are produced
Rewrite examples are client deliveries described without names.
The same discipline every time
Predictable, not an exploratory science project.
Recover the business rules
Every rule, decision point, calculation and edge case is cataloged from the existing code. That catalog becomes the specification, and it does not change.
Your approvalDesign the target
The new stack or architecture in full: component boundaries, data flows, deployment, scaling and failure modes, approved by your team before code is generated.
Your approvalBuild with parity tests
An automated suite proves the new system gives the same outputs as the old one for every business scenario, and it runs on every build.
Run side by side
For larger systems, old and new receive the same inputs and their outputs are compared. Cut-over happens only when parity is proven at scale.
Keep a way back
Every delivery includes a documented rollback plan. No change of architecture is one-way.
Self-heal: parity differences are fixed before you see them.
When a parity test shows the new system answering differently from the old, CORE traces the difference to its cause, corrects it and re-runs the comparison. You review the result, not the debugging.
- Parity tests on every build
- Differences traced to the exact rule
- Corrections re-verified automatically
- Every correction logged for review
Being clear about the boundary
When Re-engineer is not the right product.
You need new features
Adding or changing features on an architecture that is basically fine is an Optimize job.
See OptimizeThe rules themselves must change
Re-engineer preserves business logic exactly. Changing the logic is Optimize, or Create for a wholesale rethink.
See OptimizeThere is nothing to keep
If the old system holds no rules worth recovering, starting from the requirement with Create is faster.
See CreateQuestions about Re-engineer
What is the difference between a rewrite and a re-architecture?
A rewrite moves the system to a new technology stack, such as ASP to modern services or Java to .NET. A re-architecture changes how the system is built, such as moving to the cloud, splitting a monolith or adding multi-tenancy. CORE Re-engineer does both, and many projects combine them.
How does CORE preserve business rules from legacy code?
It analyzes the existing code to catalog every rule, decision point, calculation and edge case before anything is rebuilt. Your team approves that catalog, and parity tests prove the new system produces the same outputs for every business scenario.
What if the legacy code has no documentation?
That is the normal case. CORE reads the code itself, so documentation is helpful but not required. Recovered rules are presented in plain language for your subject-matter experts to confirm.
Can we roll back after cut-over?
Yes. Every Re-engineer delivery includes a documented rollback plan, and larger systems run old and new side by side until parity is proven.
Bring the system everyone is afraid to replace.
Send one requirement or one legacy module. We will return a blueprint of what the rebuilt version would look like.