19-Usage-Billing-Engine

Appearance

14.16 Cost Modeling & Infrastructure Scaling ​

1. What It Is in Plain Words ​

Cost modeling projects monthly infrastructure and third-party software expenses across different traffic tiers to ensure healthy unit economics.

2. How This Project Uses It ​

  • Current Scale (10M Events/Mo):
    • AWS ECS (2x t4g.medium containers): $60/mo
    • AWS RDS PostgreSQL (db.t4g.large): $140/mo
    • AWS ElastiCache Redis: $40/mo
    • Network & Load Balancer: $60/mo
    • Total: $\approx $340/\text{month}$
  • 100x Scale (1B Events/Mo):
    • AWS ECS (8x c7g.xlarge containers): $850/mo
    • AWS RDS PostgreSQL (db.r6g.2xlarge Multi-AZ): $1,400/mo
    • AWS ElastiCache Cluster: $350/mo
    • Bandwidth & ALB: $600/mo
    • Total: $\approx $3,200/\text{month}$

3. 30-Second Interview Answer ​

"At our current volume of 10 million events per month, our AWS infrastructure cost is approximately $340 per month. At 100x scale—processing 1 billion events per month—the infrastructure scales to approximately $3,200 per month, driven primarily by PostgreSQL Multi-AZ memory and disk IOPS. Building our own engine saves over $100,000 annually compared to third-party billing vendors who charge basis-point revenue fees."