Derric Gilling at at Moesif writes about many API metrics. Thinking of an API as a product and doing the work of an API Product manager, here are 5 from his I have paid particular attention to on projects I have worked on.
- API Usage Growth (AUG): Average number of requests per month.
- API Monthly Active Users (AMU): Count of unique consumers of the API in a month. When compared with the API Usage Growth, it can help explain whether the change in API usage is based on the increase in usage by existing customers or the acquisition of new customers.
- Time to First Hello World (TTFHW): For self-service APIs, this is an important measure of the developer experience. This measures how long it takes from a developers first visit to the products developer portal, to the first transaction using the API. Its important because it tracts not just the ease of use of the APIs but also the quality of the documentation and tutorials.
- Top Customers by Usage (TCU): It would be useful to know who are the top ten customers of the API. As with most products, we would expect to see power law behaviour in action – a small set of customers will have a disproportionate amount of usage.
- API Calls by Business Transaction (ACBT) : The number of API calls for a given business transaction is a metric that tells us something about the API design. One characteristic of good API design is that a client requires a small number of calls to perform a given transaction. From a JTBD point of view, its important to start with the business transaction as the job that the customer is trying to fulfil, and design the API to minimise the CBT required for it.