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Gold1500

System Design

Cost Modeling for Cloud

Turning a capacity estimate into a dollar figure across compute, storage, and the sneaky egress line.

5 min read · core · beat Gold to climb

From capacity to dollars

Cost modeling maps your resource estimates onto cloud prices to predict the bill. It connects engineering choices to money, which is what gets a design approved.

The main line items

  • Compute: instances per hour, scaled by server count and uptime.
  • Storage: gigabytes per month, multiplied by replication.
  • Egress: bytes leaving the cloud, often the surprise that dominates media systems.
  • Managed services: databases and queues priced per throughput or per request.

Levers that cut cost

  • Reserved or committed pricing trades flexibility for a discount.
  • Autoscaling avoids paying peak rates around the clock.
  • Caching and CDNs cut egress, frequently the largest variable cost.

Egress catches many teams off guard because it scales with traffic and is billed per gigabyte, unlike the inbound direction which is usually free.

Key idea

Cost models sum compute, storage, egress, and managed services, with egress and committed pricing the biggest levers.

Check yourself

Answer to earn rating on the learn ladder.

1. Which line item most often surprises media heavy systems?

2. How does committed or reserved pricing help?