NexaPay — Real-TimePayments Platform

NexaPay, a Tier-1 fintech processing over $2 billion in daily transactions, was running on a monolithic payment core built in 2009. Transaction latency had crept up to 4.2 seconds p99 — making real-time payment scenarios impossible and causing measurable cart abandonment in their merchant products.

The existing architecture couldn't handle burst traffic during peak periods (Black Friday, month-end settlements), leading to costly manual intervention and occasional downtime that was unacceptable for a regulated financial institution.

The final architecture is a fully event-driven payment platform running on AWS EKS, with Apache Kafka as the event backbone, PostgreSQL for transactional data with Citus for horizontal sharding, and Redis for real-time settlement state. All services communicate exclusively via events, enabling horizontal scaling of any bottleneck independently.