Top-20 global bank · 2025
Rebuilding the core of a global bank — with zero downtime.
A 40-year-old core banking platform, re-engineered as cloud-native services while 30 million customers kept banking.
68%
Lower run cost
40 ms
Payment settlement, down from 11 minutes
0
Minutes of customer downtime
The challenge
The bank's mainframe core processed every account, payment, and loan — and every change took months. Regulators were pressing on operational resilience, and digital competitors were launching products in weeks.
Our approach
- 01
Strangle, don't rewrite
We decomposed the core into 140 business capabilities and migrated them one at a time behind an event-driven integration layer.
- 02
Prove parity in production
Old and new systems ran in parallel with automated reconciliation of every transaction until results matched to the cent.
- 03
Resilience by design
The new platform runs active-active across three regions with continuous chaos testing evidenced to regulators.
The outcome
Product launch cycles fell from nine months to three weeks, real-time payments went live nationwide, and the bank decommissioned its last mainframe partition ahead of schedule.
“They rebuilt the core of our bank without a single minute of customer downtime.”
Next case study
Putting production AI on the front line of emergency care.
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