Core Banking · Case Study

From a Monolith to a Scalable, Digital Banking Platform

We replace legacy cores with a modern, cloud-native, microservices platform — delivered incrementally, module by module, with no disruptive big-bang cutover. Engineered for both conventional and Shariah-compliant banking.

1,400+

Branches

Migrated to the new core in production.

13,000+

Users

Transitioned to a modern web front end.

99.97%

Transactions

Processed on the new core at launch.

~2,400

Use Cases

Re-engineered as independent services.

The objective

Re-engineer the core from the inside

Rather than buy an off-the-shelf core from an international vendor, forward-looking banks re-engineer their core from within.

In one engagement, we helped a Tier-1 commercial bank — serving corporate, commercial, SME, agricultural, and consumer segments — replace a 20-million-line monolith of roughly 2,400 use cases with a cloud-native, microservices platform. It was designed to co-exist with the legacy system during rollout, scale horizontally, and deploy module by module across 1,400+ branches without disrupting daily operations.

The challenge

A home-grown core that had outgrown its foundations

Functionally complete, but constrained by two decades of monolithic growth.

Monolithic Architecture

~20M lines of code and ~2,400 use cases in a single, tightly coupled, reports-based application.

Documentation Debt

Two decades of incremental growth left structured documentation incomplete, slowing every new developer's ramp-up.

Legacy Presentation Layer

An applet-based client could no longer deliver modern dashboards, mobile access, or web integration.

Integration & Scaling Limits

Brittle file-based middleware and single-process architecture created data silos, concurrency limits, and single points of failure.

The solution

A platform built to last another twenty years

Our engineers worked side by side with the bank's own teams — from requirements capture through production rollout — on four guiding principles.

Co-existence Over Big-Bang

The new platform shares the same database, business checks, and UI patterns as the legacy core, rolled out module by module — Online Banking, Teller, CRM, Term Deposit, Trade Finance, Back Office — each stabilized before the next.

Open-Source First

A reactive front end, cloud-native Java microservices, event streaming, enterprise persistence, container orchestration with a service mesh, centralized IAM, and full observability — open source by default, with paid support where critical, to eliminate vendor lock-in.

Finite State Machine Architecture

Each of ~2,400 use cases is modelled as an explicit finite state machine orchestrating views, view-models, APIs, and data services — making journeys auditable, business logic visible to non-developers, and the testing surface tractable at scale.

Continuous Security

Security review is embedded in every release cycle; vulnerability classes across all microservices are continuously surveyed and findings fed back into the development model for systematic remediation.

Architecture at a glance

Five planes, one enterprise service bus

Organized around five planes — connected through an enterprise service bus to channels and external systems, with cross-cutting AAA services.

Channels

Internet Banking

Mobile Apps

Digital Channels

External

Payment Networks

Identity & AML

Enterprise Service Bus

Bank Users

API Gateway

Presentation Plane

General Banking

Trade Finance

Credits

Finance

International

Settlements

Treasury

Reports

Setup & UPM

Workflow

Services Plane

Matrix

Cards

Accounts

Instruments

Data Plane

AAA Services

Security

Authentication

Authorization

Auditing

Monitoring

Governance

Compliance

AI Compute

Same business checks · same database · same UI/UX · same business processes — full co-existence with the legacy system, modern technologies underneath.

Why build, not buy

Not bought — re-engineered

Tailored

Shaped to the bank's processes, not the other way around.

Owned

Full IP and roadmap control held by the institution.

Phased

Module-by-module rollout — no big-bang risk.

Open

Open-source defaults at every layer of the stack.

Technology stack

Open by default, at every layer

Front-End

Reactive web frameworkState managementComponent library

Back-End & Messaging

Cloud-native Java microservicesEvent streamingEnterprise RDBMSContract-first APIs

Infrastructure

Container orchestrationService meshCloud-native ingressIAMPrivate registry

DevOps & Observability

CI/CD pipelineCentralized loggingMetricsDashboards

Outcomes & impact

Modernized without a single day of downtime

99.97% on the New Core

By launch, the platform processed 99.97% of the bank's transactions across the entire branch network — module by module, without a single big-bang cutover.

1,400+ Branches Migrated

Every branch transitioned to the new core in production, without disrupting a single day of operations.

13,000+ Users Transitioned

The full active user base moved to a modern web front end with role-based access.

~2,400 Use Cases Re-engineered

Each re-implemented as a finite-state-machine-driven microservice: auditable, testable, and independently deployable.

Vendor Independence

Open-source usage across every layer removed vendor lock-in from the core itself.

Productized for Export

What began as a single engagement was productized into a platform now tailored for new markets as a credible alternative to global lending suites.

Let's build

Ready to modernize your systems?

Book a 30-minute discovery call. We'll map your roadmap — from quick wins to full transformation, in software or silicon.

Book a discovery call Explore our capabilities