Industrial Software Integration & APIs worked example

API Call Volume at 99% system uptime: a worked example

What does the result look like when system uptime reaches 99%? The full calculation is worked below with real intermediate numbers. Use this calculator when sizing an API gateway, estimating usage-based platform costs, or confirming that your REST/OPC UA/MQTT endpoint can handle the expected request volume from connected systems.

The inputs for this scenario

  • Data endpoints or tags polled: 50 endpoints (unchanged)
  • Sync cycles per period: 480 cycles (unchanged)
  • System uptime: 99 % (raised for this scenario; the documented default is 97)
  • Successful delivery rate: 98 % (unchanged)

Working through the calculation

  • Applying the documented formula (Gross API call volume = data endpoints x sync cycles per period) to the inputs above produces each figure below.
  • At this operating point the engine returns 23,285 calls for effective api calls delivered, the number this scenario is built around.
  • At this operating point the engine returns 24,000 calls for gross api call volume.
  • At this operating point the engine returns 240 calls for calls lost to downtime.
  • At this operating point the engine returns 475 calls for calls lost to errors or retries.

How this compares with the baseline

  • Against the tool's baseline example, where system uptime sits at 97% and the headline result is 22,814 calls, this scenario comes in 2.06% above the baseline at 23,285 calls.
  • A figure at this level is achievable when system uptime is genuinely sustained, not just peaked for a shift. It assumes a flat, uniform polling pattern; bursty event-driven traffic, backoff retries that multiply calls, or batched payloads will diverge from this steady-state estimate.

Results at a glance

  • Effective API calls delivered: 23,285 calls (headline result)
  • Gross API call volume: 24,000 calls
  • Calls lost to downtime: 240 calls
  • Calls lost to errors or retries: 475 calls

Run it with your numbers

  • Every input above is editable in the live API Call Volume calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.