Lars de Ridder: Advanced REST API's

published May 22, 2015

Lars de Ridder talks about Advanced REST API's, at PyGrunn.

See the PyGrunn website for more info about this one-day Python conference in Groningen, The Netherlands.

See slides at

I am head of tech a Paylogic.

Goals of REST: loose coupling between web client and server. Use existing web infrastructure.

Step 1, 2, 3: design your process.

Example with data as basis for the modeling. Simplistic database tables: CoffeeType, CupOfCoffee, Order, Barista. So you GET or POST to /coffeetype, /cupofcoffee, /order, /barista. POST will have keyword arguments, like number of cups. What is missing? You want to get the price, without ordering first.

So far, this is easy to design and build the server. But you get logic in the clients, like for the price. Tight coupling between api design and database design. Your table names should not determine your api names.

Model your process as seen from the end-user. For every step 'invent' a resource. In our case they might be /coffeetypes, /quote, /orders (or /payments), maybe /baristas. For every resource determine the relations. This is the most important parts. Never rely on urls, but use link relations. has defined standards for this. Consider which data is involved for every resource.

Media types for APIs. Standard on how to format your (JSON) response. There are standards for this, so do not reinvent the wheel. We use HAL. It is minimalistic, basically only describing how to embed information. By visiting a url you can discover other urls that you can call. Others:, Mason,,

"I don't need to write documentation, my API is discoverable." This is of course not true. Discoverable APIs help when you are developing an application that uses the API. But do document the process that apps should use.

You should learn HTTP, learn what the verbs really mean. REST really is HTTP.

We chose to evolve our API instead of versioning it, using deprecation links.