Next-generation mobile banking for a top-10 joint-stock bank

In 2021, one of Vietnam's ten largest joint-stock banks set itself a clear goal: move 70% of retail transactions to digital channels within three years. Its mobile app, first built in 2015, could no longer keep pace with the product roadmap the board expected. Zentrova was brought in to redesign both the customer experience and the platform behind it, from the login screen down to the integration layer with the core banking system.

The challenge

The legacy app was a monolith tightly coupled to the core, and every release needed six to eight weeks of testing. On payday, response times regularly exceeded eight seconds and failed transactions tripled. Opening an account online took 25 minutes, and almost half of applicants abandoned the process and went back to a branch. The bank also needed a platform its own engineers could run and extend once the programme ended, not another black box dependent on an outside vendor.

Our solution

• Microservices architecture with more than 120 APIs, separating accounts, payments, cards and lending so that each team can ship on its own schedule.
• Kafka event streaming as a buffer between the app and the core, absorbing traffic spikes without putting posting logic at risk.
• eKYC with OCR and face matching, reading ID documents and verifying biometrics directly on the customer's device.
• Layered security: device binding, end-to-end encryption, jailbreak detection and real-time transaction risk scoring, all aligned with PCI DSS.
• Kubernetes deployment with fully automated CI/CD and a nightly regression suite of more than 3,000 scenarios.
• Co-delivery model: 85 Zentrova engineers working alongside 30 bank specialists in two-week sprints, handing over operations to the in-house team step by step.

Results

The new app went live after nine months, and every customer was migrated within six weeks with no planned downtime.

• Online account opening reduced from 25 minutes to 4 minutes.
• Monthly active users reached 3.2 million, a 2.4x increase within 18 months.
• Average response time below 400 ms, even on peak days.
• App availability of 99.98%.
• Release cycle shortened from six weeks to two weeks.
• App store rating up from 2.9 to 4.7/5.

The bank's in-house team now owns day-to-day operations and ships new features independently, while Zentrova provides a small architecture and security squad under a support agreement. The same platform is being extended to small-business customers in the next phase.

What we value most is that Zentrova didn't just write software for us. They changed the way we build digital products. — Head of Digital Banking, client bank