Legacy Application Modernization
Modernise the system nobody dares to touch.
AI maps your old code, data and business rules first. Then we rebuild module by module, running alongside the legacy system, and prove parity before every switch-over.
- Zero-downtime cutovers
- AI-assisted code mapping
- Parity before switch-over
Free 30-minute call with a senior specialist. Reply within one business day. Based in Jaipur, working with businesses across India.
- Discovery callFree 30 minutes with a senior specialist
- Scoped first phaseWritten scope, timeline and fixed price
- Build with weekly demosWorking software you can see every week
- Launch and supportGo-live with your team ready, then ongoing support
What is legacy application modernization?
Legacy application modernization upgrades ageing applications, databases and integrations without stopping the business. Stack18 uses AI to map and document old code, rebuilds in reversible steps using the strangler pattern, and proves data and behaviour parity before every cutover.
You need this when…
Tap the ones that apply to you.
Legacy Application Modernization, end to end.
Each capability is delivered by the same team on the Agentic SDLC, with your approval at every critical step.
Legacy assessment
Know what you have before you change it.
- AI-assisted code and data mapping
- Dependency and risk analysis
- Retain, wrap, refactor or rebuild options
Application re-engineering
Rebuild on modern architecture.
- Strangler-pattern migration
- Modern UI and APIs
- Business rules preserved
Database and data migration
Move data safely.
- Schema redesign
- Validated migration runs
- Reconciliation reports
Integration modernisation
Replace brittle file transfers.
- API layer over legacy
- Event-driven integration
- Monitoring and alerts
Cloud re-platforming
Right architecture, right cost.
- Containerisation
- Managed databases
- Cost-optimised hosting
Knowledge capture
Documentation that stays current.
- Business rules catalogue
- Architecture docs
- Runbooks
A typical engagement, step by step.
Senior people lead every phase. Specialised AI agents on the Agentic SDLC handle the repetitive work, and nothing ships without your approval.
Map
AI-assisted analysis of code, data and integrations.
Plan
Target architecture and migration sequence.
Migrate
Module-by-module rebuild running alongside legacy.
Cut over and operate
Parity testing, switch-over, monitoring, handover.
Start small. Scale when it works.
Every engagement begins with a short, fixed-price step so you can judge the fit before committing further. See pricing.
Legacy Assessment
Teams deciding whether and how to modernise.
- Duration
- 3–4 weeks
- Pricing
- Fixed price
- AI-generated system map
- Risks and options
- Costed roadmap
Modernisation Programme
Systems ready to be rebuilt in stages.
- Duration
- 3–9 months
- Pricing
- Fixed price per phase
- Phased migration
- Parity testing
- Zero-downtime cutovers
Modernisation Pod
Large estates with many legacy systems.
- Duration
- Ongoing
- Pricing
- Monthly team
- Dedicated team
- Portfolio roadmap
- Continuous migration
What we have shipped, and what a typical engagement looks like.
Delivered projects link to the full case study. Illustrative scenarios describe typical engagements and are not named client results.
Insurance company
- Challenge
- Policy admin on a 20-year-old platform.
- What we do
- AI-assisted mapping, then module-by-module rebuild with parity tests.
8 months
Manufacturer
- Challenge
- Production planning in an unsupported desktop app.
- What we do
- Web-based replacement with migrated data and integrations.
4 months
Cooperative bank
- Challenge
- Batch file integrations failing nightly.
- What we do
- API layer and event-driven integration over the core system.
3 months
Free legacy risk assessment call
Tell us about your oldest critical system. We outline the risks, options and a realistic first step.
- Risk summary
- Rewrite, refactor or replace view
- Indicative timeline
We agree targets before we start.
Every engagement has a baseline and a target on the measures that matter to you, reported at every read-out.
Legacy Application Modernization questions.
Do we have to rewrite everything?
No. Each component is retained, wrapped with APIs, refactored or rebuilt based on value and risk.
How do you avoid downtime?
New modules run alongside the old system and traffic moves gradually, with parity tests and rollback plans.
What if nobody understands the code?
AI-assisted analysis maps code, data and rules, and our engineers verify findings with your team.
How long does it take?
Assessments take 3 to 4 weeks. Programmes run in 6 to 12 week phases, each delivering something live.
Can we move to cloud at the same time?
Yes, where it makes sense. Target architecture and hosting are designed together.
Is it fixed price?
The assessment is fixed price and each programme phase is fixed price.
Let's scope your Legacy Application Modernization project.
Tell us where you are and where you want to be. A senior specialist will reply within one business day with next steps.
- Free 30-minute consultation
- Indicative estimate after the call
- NDA available on request