API Call Volume Capacity Calculator

How to calculate API Capacity?

Capacity planning is a delicate balance between handling your average daily load and preparing for unpredictable peak bursts. It is essential to ensure that your infrastructure can manage steady streams as well as sudden surges that occur during high-traffic periods.

Peak RPS = (Daily Volume / 86,400) * Peak Multiplier * (1 + Buffer)

Using the API Capacity calculator: an example

Consider a scenario involving 100,000 active users, where each user generates an average of 50 API requests per day. To ensure system stability during spikes, we plan for a 3x peak multiplier and a 20% safety buffer.

Step-by-step calculation

1. Calculate total daily requests: 100,000 users * 50 requests/user = 5,000,000 total daily requests.
2. Determine average RPS: 5,000,000 / 86,400 seconds in a day ≈ 58 Requests Per Second (RPS).
3. Apply peak multiplier and buffer: (58 RPS * 3 multiplier) * (1 + 0.20 buffer) ≈ 208 RPS final capacity.

Frequently Asked Questions

• What is a safe buffer percentage? A 20% to 30% buffer is typically recommended for production environments to handle unexpected traffic spikes without degradation.
• How does latency affect concurrent connections? Higher latency means requests take longer to complete, which increases the number of concurrent connections your server must maintain even if RPS remains stable.
• When should I consider horizontal scaling? Horizontal scaling is advisable when a single instance consistently exceeds 70% CPU/Memory utilization or when you require high availability across regions.
• Why use a peak multiplier? Real-world traffic is rarely uniform; usage often spikes during specific hours. A multiplier ensures your infrastructure stays online during these critical windows.