Product rewrite is a gamble. Lift-and-shift just moves the debt.
A legacy product rarely fails outright. It decays. Features that once took days now take sprints. Maintenance costs climb every quarter, security and audit risk compound, and roadmaps stall as teams spend their time firefighting.
Then come the two bad options. A big-bang rewrite is a gamble that runs for years, overruns budgets, and risks the very operations it was meant to fix. A lift-and-shift simply moves the same debt to the cloud.
ONE CX modernises through a third path. We re-architect legacy systems in flight, service by service, so the product continues running while it changes underneath. Technical debt is resolved alongside delivery, with zero-downtime cutover, no data loss, and audit continuity preserved throughout.
Re-Engineer Legacy Systems, Then Keep Them Modern for Good
Both run on live systems, cloud-ready, with zero-downtime cutover and no data loss.
A leading US telemedicine platform
Turned a monolith into Java microservices, API latency down ninety per cent and feature rollouts twice as fast across appointments and records.
A global luxury auction house
Turned manual, penalty-prone invoicing into an audit-ready automation layer on a live finance backbone, ML capture and PO-matching, human-in-the-loop.
Re-Engineer Legacy Systems, Then Keep Them Modern for Good
Both run on live systems, cloud-ready, with zero-downtime cutover and no data loss.
Application Re-Engineering
We restructure legacy monoliths into modern, cloud-ready microservices so teams ship faster and scale on demand.
Continuous Modernisation
We treat modernisation as a continuous service, clearing tech debt alongside delivery so your product never drifts into legacy.
"Modernisation is not about new architecture.
It is about whether the business ever has to stop.
Decathlon's search layer. Dentulu's platform core. State Street's systems. Each one rebuilt at scale while the business kept running.
The principle never changes: you rebuild underneath while everything keeps running, you don't lose data, and you hand back something the client actually owns. If you need to switch the lights off, it isn't modernisation. It's a restart."
- Vaibhav Miglani, Engineering Manager - ONE CX
Architecture and Stack We Modernise On
Architecture and Stack We Modernise On
Architecture-led and stack-agnostic, our pick follows your system, your risk tolerance and your team, never a rip-and-replace by default.
Architecture We Modernise To
Strangler-Fig Migration
Our pick when the system must modernise in flight, one piece at a time, never a big-bang rewrite.
A Clean Break From the Legacy
Monolith Into Microservices
Zero-Downtime Cutover
Cloud-Native and Containerised
Reversible Releases
Secure and Defensible by Design
Stack We Modernise On
Cloud platforms: AWS, GCP, Azure, managed services and India regions
Our pick follows your data-residency duty and existing footprint, never a partner preference
Containers and orchestration: Docker, Kubernetes, EKS, GKE, AKS
Runtimes and frameworks: Node.js, Java and Spring, Go, Python, current PHP
Event streaming and messaging: Kafka, Pub/Sub, RabbitMQ, SQS
Data and migration: PostgreSQL, MySQL, MongoDB, Redis, with change-data-capture and migration tooling such as Debezium and AWS DMS
API gateway and service mesh: Kong, Istio
CI/CD and infrastructure as code: GitHub Actions, GitLab CI, ArgoCD, Terraform
Observability: Datadog, Grafana, Prometheus, OpenTelemetry
Why India's CPOs, CIOs and CDOs Choose ONE CX to Modernise
01
One Team Modernises It in Flight, Then Runs It
We re-engineer the system while it keeps running, then run it after cutover. One team, never a hand-off
One Team Modernises It in Flight, Then Runs It
We re-engineer the system while it keeps running, then run it after cutover. One team, never a hand-off
02
We Modernise Without Freezing Your Roadmap
A rewrite that freezes features costs you the market. We clear tech debt alongside delivery, shipping while we split the monolith, so rollouts run twice as fast.
We Modernise Without Freezing Your Roadmap
A rewrite that freezes features costs you the market. We clear tech debt alongside delivery, shipping while we split the monolith, so rollouts run twice as fast.
03
Zero Data Loss, Audit Continuity Preserved
We cut over with old and new running in parallel, reconciled daily, so no record is lost and the audit trail holds.
Zero Data Loss, Audit Continuity Preserved
We cut over with old and new running in parallel, reconciled daily, so no record is lost and the audit trail holds.
04
Your Team Keeps Ownership, in Its Own Language
We re-engineer the system while it keeps running, then run it after cutover. One team, never a hand-off. We modernise in your team's ecosystem where it matters, not a rewrite that orphans them.
Your Team Keeps Ownership, in Its Own Language
We re-engineer the system while it keeps running, then run it after cutover. One team, never a hand-off. We modernise in your team's ecosystem where it matters, not a rewrite that orphans them.
05
No Lock-In, the Modern Code Is Yours
You own clean, documented, modern code and the architecture behind it. Keep us to run it, take it in-house, or move on. No black box, no rented platform you cannot leave.
No Lock-In, the Modern Code Is Yours
You own clean, documented, modern code and the architecture behind it. Keep us to run it, take it in-house, or move on. No black box, no rented platform you cannot leave.
06
Proven on the Systems Businesses Run On
We have re-engineered the systems businesses run on: a global auction house's finance backbone, a healthcare core, a gaming platform at peak load. Not side projects.
Proven on the Systems Businesses Run On
We have re-engineered the systems businesses run on: a global auction house's finance backbone, a healthcare core, a gaming platform at peak load. Not side projects.
Product Modernisation FAQs for India's CPOs and CIOs
How is Product Modernisation different from Product Engineering and Platform Engineering?
Product Modernisation transforms systems you already run. Product Engineering builds new products and platforms from scratch; Platform Engineering builds the backend and infrastructure underneath them. We take an existing, ageing system and re-architect, re-engineer and replatform it into a modern one, in flight. If you are building something new, that is our Product Engineering practice. If you are transforming what already exists, that is us. A configured platform such as Salesforce, HubSpot or a packaged CDP is not something you re-architect; migrating, consolidating and re-implementing it is our Martech Solutions practice, and the pipelines and customer-data platform underneath are Data Engineering.
Do you modernise our martech, CRM or data stack?
It depends on whether it is bespoke software or an off-the-shelf platform. A custom, in-house system someone built years ago, we modernise. A configured platform such as Salesforce, HubSpot or a packaged CDP is not something you re-architect; migrating, consolidating and re-implementing it is our Martech practice, and the pipelines and customer-data platform underneath are Data Engineering. The test is a custom-engineered system versus a configured product.
Can you modernise a live system without downtime, and how do you keep DPDP and audit continuity?
Yes. We run the old and new systems in parallel, writing to both and reconciling daily, then switch over once the new one is proven, a single cutover with no data loss and no interruption. Security and data residency are designed in from the first commit, so the audit trail holds end to end and data stays within the residency your obligations require.
What actually changes when you move a monolith to microservices?
A monolith is one large codebase where every change risks the whole system. Microservices split it into independently deployable parts, each owning its data, so teams ship in parallel without colliding and one fault no longer takes everything down.
Do you use AI to modernise faster?
Yes, to accelerate the work, not as the product. AI helps us map a legacy system's dependencies, make sense of undocumented code, and refactor faster, which shortens the slowest phases of modernisation. We do not sell AI models; every AI-assisted change is reviewed and tested, so speed never costs us correctness or the audit trail.
Do we own the modernised code, and are we locked in?
You own it. We hand over clean, documented, modern code and the architecture decisions behind it, built in your stack. Keep us on to run it, take it in-house, or move to another partner. No black box, no rented platform you cannot leave.
How long until the first modernised service ships?
Our average is a first modernised service in production inside ninety days, chosen to retire real risk or unblock the roadmap early, not a year of planning before anything ships. From there we modernise service by service while the system keeps running. We do not claim the full timeline at the start; we prove it in delivery.
Stop Pouring Budget Into Legacy That Holds You Back. Start Shipping Again. A thirty-minute scoping call: which system, what it is costing you in maintenance and lost velocity, and what the first ninety days modernise. No commitment.