Build & Modernize
Legacy Modernization
The system your business runs on stops being a hiring problem and a security liability.
What this engagement is
Legacy rewrites fail when the specification is the old code and nobody reads it. The business rules that matter — the discount logic added in 2009, the edge case handling a discontinued product line — live in the running system, not in any document. A rewrite that ignores that discovers the rules one production incident at a time.
We start by pinning down observable behavior: inputs, outputs, edge cases, and the undocumented rules embedded in stored procedures and batch jobs, captured as executable characterization tests. The rewrite then has a definition of correct that doesn't depend on institutional memory. Each module is rewritten on a currently supported stack and verified against the captured behavior before the next one starts.
Delivery is phased and independently verifiable. During the parallel-run period, old and new systems process the same live inputs and we reconcile every difference until output matches for an agreed stretch. Cutover happens when the evidence says it's safe, not when the calendar says it's time. You end with a modern system, the test suite that defines its behavior, and documentation your next hire can actually use.
Who this is for
- Businesses running critical processes on a platform they can no longer hire for
- Systems blocking a compliance requirement or an integration you need
- Organizations where a single retirement would be an operational emergency
What you get
- Characterization test suite documenting current behavior
- Modernized system on a currently supported stack
- Parallel-run period with output reconciliation
- Data migration scripts, run and verified
- Architecture documentation and developer onboarding guide
Scope
Exactly what the quoted price covers
The scope document for this engagement lists both columns below in writing. Nothing moves between them without a conversation.
Included in the engagement
- Characterization tests for all agreed modules, including undocumented business rules
- Module-by-module rewrite on a stack we agree together
- Data migration scripts with verification runs against production copies
- Parallel run with difference reconciliation and a written cutover report
- Deployment pipeline, monitoring, and rollback procedure for the new system
Not included
- New features beyond the current system's behavior — scoped separately if wanted
- Modernizing systems other than the one in scope, even if they integrate with it
- Replatforming adjacent infrastructure (network, identity, email)
Working together
What we need from you
Fixed dates only hold when both sides show up. These are the commitments we ask for in exchange for ours.
- 01
Access to the production system, its database, and whoever currently maintains it
- 02
One person from the business side who can confirm what correct output looks like
- 03
A frozen feature list on the legacy system for the duration of the parallel run
Process
How it runs
- 01
Behavior capture
Current behavior documented as tests, including the undocumented rules. This becomes the contract for the rewrite.
- 02
Phased rewrite
Module by module on the new stack, each verified against the captured behavior before the next one starts.
- 03
Parallel run
Both systems process live inputs. Differences are reconciled until output matches for an agreed period.
- 04
Cutover and handover
Switch, monitor, and hand over documentation, tests, and deployment tooling.
Scope a legacy modernization engagement.
Send us the situation in a few sentences. You'll get a scope, a price, and a date back — or an honest no.