When API requests are made one-after-the-other they'll quickly hit rate limits and when that happens:

If you provide an API client that doesn't include rate limiting, you don't really have an API client. You've got an exception generator with a remote timer.

— Richard Schneeman Stay Inside (@schneems) June 12, 2019

That tweet spawned a discussion that generated a quest to add rate throttling logic to the platform-api gem that Heroku maintains for talking to its API in Ruby.

If the term "rate throttling" is new to you, read Rate limiting, rate throttling, and how they work together

The Heroku API uses Genetic Cell Rate Algorithm (GCRA) as described by...

Over the last few years, GraphQL has emerged as a very popular API specification that focuses on making data fetching easier for clients, whether the clients are a front-end or a third-party.

In a traditional REST-based API approach, the client makes a request, and the server dictates the response:

$ curl https://api.heroku.space/users/1 { "id": 1, "name": "Luke", "email": "luke@heroku.space", "addresses": [ { "street": "1234 Rodeo Drive", "city": "Los Angeles", "country": "USA" } ] } 

But, in GraphQL, the client determines precisely the data it wants from the server....

Heroku has many public API endpoints. Each of these endpoints needs to be tested so that we know how they work, and documented so that our customers (and other API consumers) know how they work. Follow along, and we’ll learn how Heroku uses JSON Schema to test and document our Platform API – and how it helped us uncover an unexpected bug, rooted in the way the Oj gem parses Big Decimals.

JSON Schema files are like blueprints that define the structure and semantics of other JSON documents. When a JSON Schema file is applied to a JSON document, you can determine whether the document is valid (conforms to the schema) or is invalid (does not conform to the schema).

So how do we at Heroku use...

This is the first in a series of blog posts examining the evolution of web app architecture over the past 10 years. This post examines the forces that have driven the architectural changes and a high-level view of a new architecture. In future posts, we’ll zoom in to details of specific parts of the system.

The standard web application architecture suitable for many organizations has changed drastically in the past 10 years. Back in Heroku’s early days in 2008, a standard web application architecture consisted of a web process type to respond to HTTP requests, a database to persist data, and a worker process type plus Redis to manage a job queue.

How to blend a rock-solid CMS and API with the absolute best in front-end tooling, built as a single project and hosted seamlessly on Heroku.

Rails is an incredible framework, but modern web development has moved to the front-end, meaning sometimes you don’t need all the bulk of the asset pipeline and the templating system. In Rails 5 you can now create an API-only Rails app, meaning you can build your front-end however you like—using Create React App, for example. It’s no longer 100% omakase.