Core Banking · Microservices Migration

CBS Modernisation:
Monolith to Microservices

Ongoing
Banking client

An ongoing modernisation programme. Out of many modules in this core banking system, we have completed the architecture and development of 5 modules, now running independently in production.

5
Modules in production
Event
Driven via RabbitMQ
0
Data loss events
Full
Audit trail compliance
Completed modules

Investment module first, because sequencing matters

Module 1
Investment
Bank-facing internal transaction flows. Chosen first to reduce external risk. Forms the dependency base for all subsequent modules.
Modules 2 & 3
AML + FRM Phase 1
Migrated based on Investment dependency. Own databases, event-driven integration, full Financial Risk Management audit trail.
Modules 4 & 5
User Mgmt + Scroll Mgmt
Identity/auth service plus financial document management, fully decoupled with own data stores and event-driven sync.
Architecture Diagram

Monolith decomposition: 5 modules extracted and live

Each microservice owns its own database and communicates exclusively via RabbitMQ. Idempotent consumers ensure zero data loss even on retry. 5 modules in production with more in design.

LEGACY MONOLITH (BEING DECOMPOSED) CORE BANKING MONOLITH: tightly coupled modules being decomposed one by one Investment ✓ Extracted AML ✓ Extracted FRM Ph.1 ✓ Extracted User Mgmt ✓ Extracted Scroll Mgmt ✓ Extracted FD·G-Sec Next... MICROSERVICES (IN PRODUCTION) Investment Own DB Event publisher Audit logged AML Own DB Consumes events Idempotent FRM Phase 1 Own DB Risk event audit RBAC enforced User Mgmt Own DB Auth tokens Service identity Scroll Mgmt Own DB Doc management Event-driven sync EVENT BUS RabbitMQ EVENT BUS Idempotent consumers · Retry with backoff · Dead-letter queues · At-least-once delivery DEDICATED DATABASES DB: Investment Isolated schema DB: AML Isolated schema DB: FRM Isolated schema DB: Users Auth tokens DB: Documents Isolated schema Deployed as independent .NET executables on AWS Windows VM · Docker containerisation POC completed
Tech stack

Production-grade engineering stack

.NETRabbitMQAWS Windows VMEvent-drivenIdempotent consumersRBACAudit logging

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