Overview
We replatformed a brittle, monolithic subscription-billing system into a convergent, event-driven microservices core — handling real-time provisioning, renewals, charging, and reconciliation for millions of VAS subscribers. The migration was executed with a dual-write, zero-downtime cutover so revenue never paused.
The challenge
The operator’s 12-year-old billing monolith was failing under load, mis-charging subscribers, and blocking every new product launch. Any modernisation had to happen without dropping a single billing event or taking the platform offline.
Our approach
We modelled the billing domain into bounded services on a Kafka backbone, introduced a dual-write phase to keep old and new systems in sync, and migrated traffic behind feature flags. Idempotent processing and a full reconciliation suite guaranteed billing accuracy throughout the cutover.
Outcomes
- 8,000 transactions per second sustained
- 99.99% billing accuracy post-migration
- 35% lower cost-to-serve
- Zero downtime during cutover