How We Built a Real-Time Credit Card Fraud Detection System: An Architect's Perspective

Every millisecond counts when it comes to fraud. A fraudulent transaction approved in 200ms costs real money. A legitimate transaction declined in 200ms costs a customer. Getting this balance right — at scale — is one of the hardest engineering problems in financial services. This is a deep dive into the architectural decisions, trade-offs, and hard lessons from building a production-grade credit card fraud detection system. No toy datasets. No Jupyter notebooks. Real architecture, real constrai