[guide]
API and Server Cost Guide
Server cost should be evaluated together with usage, external API spend, database cost, storage, CDN, monitoring, and revenue per user. This helps avoid pricing a product below its operating cost.
Core formula
Total monthly cost = request-based external API cost plus fixed hosting, database, storage, CDN, logs, monitoring, and other operations costs.
Break-even users
Break-even paid users = total monthly cost divided by revenue per user after payment fees. This shows how many paying users are needed before infrastructure is covered.
What to watch
Usage spikes, background jobs, logs, database backups, egress, and managed service minimum charges can matter more than the web server price.
Limit
Cloud pricing changes by region and product tier. Confirm official AWS, GCP, Vercel, or vendor pricing before committing.
Worked example
Suppose a product has 1,000 monthly active users and each user makes 500 requests. At 5 KRW per external API
call, 500,000 requests cost 2,500,000 KRW. Adding 30,000 KRW for hosting, 50,000 KRW for the database, 10,000
KRW each for storage and CDN, and 20,000 KRW for monitoring produces a 2,620,000 KRW monthly infrastructure
estimate.
That works out to 2,620 KRW per active user. A 9,900 KRW subscription with a 3.3% payment fee contributes
about 9,573 KRW before infrastructure, so roughly 274 paying users are needed to cover this example's monthly
infrastructure cost. The result is a cost floor, not a full company break-even point, because payroll,
support, sales, taxes, refunds, and other overhead are outside the calculator.
Build a cost model that survives growth
Separate fixed and variable cost
Hosting minimums may stay flat while API calls, database operations, storage, and egress grow with usage. Keeping them separate makes scaling assumptions visible.
Use billed traffic
Background jobs, retries, health checks, bots, and cache misses can create billable work that is not represented by product analytics alone.
Include resilience
Production budgets may need backups, multiple zones, observability, security services, and spare capacity. A single test instance is not a complete production estimate.
Review the bill monthly
Replace assumptions with invoiced amounts and usage metrics, then compare forecast and actual cost. Large differences usually reveal a missing workload or pricing tier.
Open the API/server cost calculator