I am implementing public API using Google Cloud Endpoints & Google Cloud Functions. This API will later be used in web application, and I need a way to throttle number of requests to prevent people from flooding API with huge number of requests, which could increase project maintenance costs. I don't care if API becomes unavailable due to throttling, protecting myself from those costs takes higher priority.
What should I do or which tools should I use to achieve this on Google Cloud?
If we look at the Google Cloud Endpoints documentation in the section called About Quotas we will find a description of a capability to limit the number of requests from calling applications. The article then goes into depth on how to set it all up which appears to be to add additional attributes to your API's exposed Open API spec.
There is also a great article called Rate-limiting strategies and techniques that provides a rich set of alternatives and thoughts. My suggestion would be to read this article in depth which will arm you with an overview of each of the choices at your disposal. There is also a rich set of additional references at the end of the article for further reading.
