# Bank Cloud and Application Rationalisation — Enterprise Architecture Case

## Context
A multi-market bank needed to reduce technology cost while modernising customer and risk platforms. Its estate contained overlapping applications, inconsistent cloud controls, and several critical workloads approaching end of support.

## Architecture challenge
- 430 applications across on-premises and two cloud providers
- Duplicate customer, reporting, integration, and document capabilities
- Regulatory residency, operational resilience, and audit constraints
- Cloud migrations planned without application disposition or dependency evidence

## Assessment method
Applications were scored against business fit, technical health, cost, risk, data sensitivity, resilience tier, integration complexity, and strategic alignment. Dependency mapping identified migration groups and shared platform blockers.

## Target architecture
The target uses governed cloud landing zones, reusable security and observability services, domain-aligned APIs and events, and a controlled data platform. Systems of record remain isolated by jurisdiction where required; shared analytical products use approved, lineage-tracked data movement.

## Portfolio decisions
- **Retain:** stable systems with strong fit and acceptable lifecycle
- **Rehost:** low-change workloads with urgent infrastructure risk
- **Replatform:** workloads benefiting from managed runtime and database services
- **Refactor:** strategically differentiating services with scalability constraints
- **Replace:** commodity capabilities better served by a packaged platform
- **Retire:** duplicate or unused applications after data-retention controls

## Transition plan
1. Establish landing zones, identity, policy, logging, and recovery controls.
2. Remediate end-of-support and critical resilience gaps.
3. Move applications in dependency-aware waves by business domain.
4. Consolidate integration and data services as workloads migrate.
5. Retire infrastructure only after application, data, and control sign-off.

## Measures
- Applications retired and annual run-cost removed
- Critical lifecycle risks closed
- Migration lead time by disposition
- Resilience-test pass rate and recovery performance
- Cloud policy compliance and unit cost by domain

*This is a representative, anonymised EAOT reference case. Figures and system names illustrate a realistic enterprise scenario rather than a named client engagement.*