Core Banking Architecture Diagram

Decoupling a Legacy Core Banking Monolith with Event-Driven Settlement Rails

A Tier-2 retail bank faced critical throughput ceilings, 4-hour batch settlement windows, and recurring downtime during peak transaction cycles on an on-premise legacy core.
Codixon engineered a non-disruptive modernization strategy using the Strangler Fig pattern, replacing brittle batch jobs with an asynchronous, event-streamed ledger architecture that slashed settlement latency by 84%.
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Executive Impact

Key Delivery Outcomes

Measurable performance, latency, and operational improvements delivered across the core transaction estate.

84 %
Latency Reduction Clearing & settlement dropped from 4h to <38m
100 %
Uptime Target Zero unplanned outages across 18 months
12000 +
Peak TPS Handled High-concurrency sustained retail volume
100 %
Data Integrity Deterministic ledger consistency across dual runs
Technical Constraints

The Legacy Monolith Bottleneck

Over two decades of coupled stored procedures, single-instance database locks, and nightly batch runs severely limited digital product agility.

Cascading Database Deadlocks

Concurrency

Concurrent account balance locks during end-of-day reconciliation triggered high checkout failure rates across mobile and online banking channels.

Brittle Nightly Batch Processing

Batch Dependency

Over 400 interconnected COBOL and PL/SQL jobs had to execute sequentially; a single job failure delayed clearinghouse transmission windows.

Deployment Freeze Windows

Deployability

Deploying simple ledger adjustments required scheduled maintenance windows with weekend core downtime and manual rollback scripts.

Regulatory Reporting Friction

Compliance

Generating auditable transaction snapshots required querying active production tables, risking operational throughput during business hours.

Engineering Blueprint

Strangler Fig Decoupling & Event Rails Architecture

A deterministic, phased migration model that extracted transactional capabilities without impacting live core operations.

01
EXTRACTION

Change Data Capture & Event Sourcing

Implemented Debezium-based CDC pipelines on database transaction logs, streaming state changes into Apache Kafka without querying core operational tables.

02
ISOLATION

Read-Side CQRS Materialization

Constructed low-latency read models using Redis and PostgreSQL, offloading 92% of balance-check and history queries away from the legacy relational core.

03
ORCHESTRATION

Asynchronous Settlement Workflows

Developed domain-driven microservices running on private Kubernetes clusters to govern settlement rules, clearing validation, and ledger reconciliation.

04
CUTOVER

Deterministic Dual-Run Cutover

Executed dual-write ledger shadow testing across 60 banking days to mathematically verify settlement equivalence before decommissioning legacy stored procedures.

Technology Matrix

Production Engineering Stack

Zero-downtime, event-driven infrastructure engineered for strict transactional consistency and sub-second settlement.

Event Streaming & Messaging
Apache Kafka
RabbitMQ
gRPC / Protobuf
Services & Execution
.NET 9 / C#
Go
Kubernetes (K8s)
Docker Containers
Persistence & Caching
PostgreSQL
Redis
Amazon Web Services
Observability & Infra
Datadog / Prometheus
OpenTelemetry
Grafana / Prometheus
Terraform
Verified Business Impact

Decoupled Architecture, Enterprise-Grade Reliability

"Codixon's principal architects transitioned our core settlement engine from an unstable batch process to a resilient, event-streamed backbone without a single minute of banking downtime. Our engineering velocity and release confidence have transformed completely."
M
Marcus Vance
Chief Technology Officer , Tier-2 Regional Retail Bank
Key Business Results

Measurable Organizational Impact

  • Eliminated $1.2M in annual proprietary mainframe licensing and legacy compute overhead.
  • Reduced scheduled core maintenance downtime from 16 hours per month to zero.
  • Achieved fully automated, real-time auditability satisfying strict central bank compliance mandates.
  • Shortened new financial product release and API deployment cycles from 9 months to 3 weeks.
Legacy Modernization Strategy

Modernize Your Core Systems Without Operational Disruption

Partner with dedicated enterprise architects to eliminate legacy bottlenecks, transition to event-driven architectures, and establish zero-downtime reliability.

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  • Non-disruptive Strangler Fig migration methodology
  • Deterministic dual-run validation guarantees zero ledger discrepancy
  • Complete repository, pipeline, and infrastructure ownership handover