Services · Modernization

Legacy Modernization

Retire technical debt without stopping the business.

We modernise ageing applications, databases and integrations in safe, reversible steps, using AI to map and document old code so nothing is lost, and proving parity before every switch-over.

  • Zero-downtime cutovers
  • AI-assisted code mapping
  • Proven parity
Book a free consultation →See how we work

Free 30-minute call with a senior modernisation architect. Reply within one business day. Based in Jaipur, working with businesses across India.

AImaps and documents legacy code
0big-bang switch-overs
Paritytested before every cutover
Quick answer

What is legacy application modernization?

Legacy application modernization is upgrading ageing applications, databases and integrations without stopping the business. Stack18 works in safe, reversible steps, using AI to map and document old code so nothing is lost, and proves parity before every switch-over.

Is this you?

You need Legacy Modernization when…

Tap the ones that apply to you.

Most teams we work with recognise two or three of these.

Talk to an expert about this
What we deliver

Legacy 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 exactly what you have before you change it.

  • AI-assisted code and data mapping
  • Dependency and risk analysis
  • Modernisation options and costs

Application re-engineering

Rebuild on modern architecture, module by module.

  • Strangler-pattern migration
  • Modern UI and APIs
  • Business rules preserved

Database & data migration

Move data safely to modern databases.

  • Schema redesign
  • Validated migration runs
  • Reconciliation reports

Integration modernisation

Replace brittle file transfers and point-to-point links.

  • API layer over legacy
  • Event-driven integration
  • Monitoring and alerts

Cloud re-platforming

Move to cloud with the right architecture.

  • Containerisation
  • Managed databases
  • Cost-optimised hosting

Knowledge capture

Living documentation so knowledge never sits with one person again.

  • Business rules catalogue
  • Architecture documentation
  • Runbooks
How we work

A typical Legacy Modernization engagement, week by week.

Senior people lead every phase. Specialised AI agents on the Agentic SDLC handle the repetitive work, and nothing ships without your approval.

01Weeks 1–3

Map

AI-assisted analysis of code, data and integrations.

You getSystem map, rules catalogue
AgentsCompassLedger
02Weeks 3–4

Plan

Target architecture and migration sequence agreed.

You getMigration plan
AgentsBlueprint
03Weeks 4–16

Migrate

Module-by-module rebuild running alongside legacy.

You getModern modules live
AgentsWeldGridWatch
04Weeks 16–18

Cut over

Parity testing, data migration and switch-over.

You getLegacy retired
AgentsLaunch
05Weeks 18–22

Operate

Monitoring, optimisation and handover.

You getRunbooks, reports
AgentsPulse
Ways to engage

Start small. Scale when it works.

Every engagement begins with a short, fixed-price step so you can judge the fit before committing further.

Start here

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
Start with Legacy Assessment
Most common

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
Discuss Modernisation Programme
Long-term

Modernisation Pod

Large estates with many legacy systems.

Duration
Ongoing
Pricing
Monthly team
  • Dedicated team
  • Portfolio roadmap
  • Continuous migration
Discuss Modernisation Pod
Free for qualified businesses

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
Request your free legacy risk assessment call
Outcomes we measure

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.

Change lead timebefore vs after
Run costhosting and licences
Incidentsper month
Code coverageby automated tests
Data parityrecords reconciled
Knowledge riskpeople-dependent components
Typical engagements

Where Legacy Modernization makes the biggest difference.

Typical engagement

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

Typical engagement

Manufacturer

Challenge
Production planning in an unsupported desktop app.
What we do
Web-based replacement with migrated data and integrations.

4 months

Typical engagement

Cooperative bank

Challenge
Batch file integrations failing nightly.
What we do
API layer and event-driven integration over the core system.

3 months

FAQ

Legacy Modernization questions.

Ask us anything
Do we have to rewrite everything?

No. We assess each component and choose to retain, wrap with APIs, refactor or rebuild, based on value and risk.

How do you avoid downtime?

New modules run alongside the old system and traffic moves over gradually, with parity tests and rollback plans.

What if nobody understands the old code?

AI-assisted analysis maps the code, data and business rules, and our engineers verify the findings with your team.

How long does modernisation take?

Assessments take 3–4 weeks. Programmes run in phases of 6–12 weeks, each delivering something live.

Can you modernise to cloud at the same time?

Yes, where it makes sense. We design the target architecture and hosting together.

Do you provide legacy modernization in Jaipur and across India?

Yes. Stack18 is headquartered in Jaipur, Rajasthan, and delivers legacy modernization for businesses across India. You get a free 30-minute call, a fixed-price first step and working software every week, so the engagement works the same whether you are in Jaipur or elsewhere.

Related

Often combined with.

Modernization usually involves several moving parts: cloud and DevOps engineering for migration and hosting, enterprise software development to rebuild core systems, and technology consulting to decide what to keep, replace or retire. If an ageing ERP is the problem, Business OS is a ready replacement to evaluate. Browse all Stack18 services.

Modernization

Cloud & DevOps

Ship faster on cloud you can trust, and afford.

Explore →Product Engineering

Enterprise Software Development

Enterprise software that meets the bar for scale, security and audit.

Explore →Strategy & Consulting

Technology Consulting

Technology strategy that ends in shipped systems, not slide decks.

Explore →Accelerate with a pre-built solution

Business OS

Sales, purchase, stock, accounts and payroll in one ERP. Start from a production-ready base instead of a blank page.

See editions and prices →
Start a conversation

Let's scope your Legacy Modernization project.

Tell us where you are and where you want to be. A senior modernisation architect will reply within one business day with next steps.

  • Free 30-minute consultation
  • Indicative estimate after the call
  • NDA available on request

Tell us about your project

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