Zero-Downtime Datacentre Exit: How Zopa Bank Migrated 40% of Core Workloads to AWS in Six Months
Facing an immovable six-month datacentre lease deadline, Zopa partnered with Build Circle to migrate 120+ databases, 60TB of sensitive financial data, and 43 microservices to AWS—beating budgeted cloud costs by £420,000 and unlocking over £700,000 in recurring annual savings.
"Migrating 40% of our production banking estate under an immovable six-month deadline required exceptional engineering precision. Build Circle provided the technical leadership and execution discipline needed to eliminate our datacentre dependencies without disrupting daily banking operations."
Peter Donlon, Chief Technology Officer, Zopa Bank
Recurring annual savings unlocked by exiting legacy datacentres
Zero-downtime migration completed ahead of lease expiry
Saved from budgeted cloud costs via aggressive SQL optimisation
Regulated financial data & databases safely transitioned to AWS
The Challenge
An immovable lease deadline and 40% of the bank's core estate
As one of the UK’s leading digital banks, Zopa operates under strict regulatory oversight, demanding rigorous change-control governance for any modification to production environments.
While modernising its infrastructure, Zopa faced an urgent commercial and technical hurdle. Approximately 40% of the bank's operational workloads remained tied to an on-premise physical datacentre.
The estate represented significant complexity and risk:
- Massive, high-stakes data footprint: Over 120 production databases holding 60TB of critical customer and transaction records running across MS SQL Server 2016.
- Interdependent services: 43 .NET services powering 13 distinct lines of business, alongside vital back-office applications and legacy Distributed File System (DFS) servers.
- The commercial deadline: The on-premise datacentre carried a significant annual running cost, with the physical facility lease expiring in just six months. Failing to vacate and decommission all services in time would trigger severe financial penalties and lease extension liabilities.
Zopa required senior engineering leadership capable of executing a zero-fault, highly audited migration at speed, without impacting live banking services or failing regulatory change-control standards.
The Solution
Parallelised migration tracks and hands-on technical governance
Build Circle deployed an autonomous delivery pod spanning technical leads, DevOps specialists, database administrators (DBAs), and full-stack engineers, supported directly by Build Circle Technical Directors to drive architectural alignment and unblock critical path risks.
The migration was divided into three parallel workstreams, executed iteratively to isolate risk and ensure continuous validation:
1. High-scale SQL & database transition
- Granular database migration: Orchestrated the migration of 120+ databases and 60TB of live transactional data from legacy on-premise MS SQL Server 2016 instances into scalable AWS cloud environments.
- Aggressive cloud optimisation: The database team restructured resource allocations and licensing models, cutting £420,000 from Zopa's budgeted AWS expenditure.
2. Line-of-business application modernisation
- Iterative service migration: Transitioned 43 .NET services supporting 13 line-of-business applications on an individual, phased basis.
- Zero production downtime: Engineered deployment pipelines and cutover protocols to maintain seamless uptime across live digital banking functions, meeting all internal compliance and audit thresholds.
3. Core supporting infrastructure & modern file storage
- Retiring legacy DFS: Modernised legacy back-office storage by replacing fragile on-premise Distributed File System (DFS) servers with AWS FSx.
- Resilience by design: Upgraded back-office and operational tooling into resilient, managed cloud services that eliminated single points of failure and streamlined operational overhead.
Business Outcomes
Significant bottom-line efficiency and future-proof scalability
Completed entirely within the aggressive six-month window, the programme successfully vacated the datacentre and delivered lasting commercial and technical value:
- £700,000+ recurring annual savings: Fully decommissioned the legacy datacentre, eliminating the annual overhead and locking in substantial recurring operational savings.
- 100% lease penalty avoidance: Hit every audit, regulatory, and technical milestone on time, allowing Zopa to exit the physical facility cleanly before lease expiry.
- Modernised banking foundations: Replaced legacy on-premise dependencies with a scalable, highly observable AWS footprint capable of supporting Zopa’s rapid digital banking expansion.
- Enhanced operational resilience: Upgrading from legacy DFS file systems to AWS FSx drastically improved platform reliability, backup speed, and disaster recovery capability across critical back-office operations.
Facing complex legacy migrations or tight datacentre exit deadlines?
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