Zero-Downtime Core Banking Migration to Azure
A 20-Year-Old Monolith Holding Back Growth
The bank's core banking system — built on on-premises mainframes over two decades — was struggling to keep pace with digital-first competitors. Batch processing windows stretched to 6 hours nightly, new product launches took 4–6 months, and the infrastructure cost ₹120 Cr annually to maintain. Any migration had to be executed with zero customer-facing downtime across 18 million accounts.
Strangler Fig Migration with Live Traffic Shadowing
SkySync designed a strangler fig migration pattern — incrementally replacing monolith modules with Azure-native microservices while running both systems in parallel. A custom traffic-shadowing layer replicated every production transaction to the new stack for 90 days before cutover, allowing exhaustive validation without risk.
Discovery & Architecture Blueprint
8-week deep-dive into transaction flows, data models, and regulatory constraints. Produced a 340-page migration blueprint approved by RBI auditors.
Parallel Build & Shadow Testing
Built Azure microservices alongside the live mainframe. Shadow-tested 100% of production traffic for 90 days, achieving 99.997% parity before any cutover.
Phased Module Cutover
Migrated 14 core modules in 6 phased waves over 7 months, each with automated rollback triggers and 24/7 SkySync war-room support.
Real-Time Fraud Layer
Deployed Azure Stream Analytics + custom ML models for real-time fraud scoring on every transaction — a capability impossible on the legacy stack.
Azure-Native, Event-Driven Core
Azure Kubernetes Service (AKS)
Microservices orchestration for 14 core banking modules
Azure Service Bus + Event Hubs
Decoupled inter-service communication and real-time event streaming
Azure SQL Hyperscale + Cosmos DB
ACID-compliant transactional data with global distribution
Azure ML + Stream Analytics
Real-time fraud detection scoring every transaction in <50ms
Azure Key Vault + Defender for Cloud
End-to-end encryption, secrets management, and threat detection
Azure Monitor + Datadog
Full-stack observability with sub-minute alerting SLAs
Measurable Impact from Day One
"SkySync's shadow-testing approach gave our board the confidence to approve a migration we'd been deferring for five years. The zero-downtime cutover was nothing short of extraordinary."
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