Can I use POST request to read and transform data?

Question

I'm developing an API that given a few parameters, reads the given data, transforms it and returns it as JSON.

Eg. (some logic included)

Request:
POST /myApi/exportAsText
Content-Type: application/json
{
    section: array,
    answers: array,
    targetLevel: int
}

Output:

// Goes through data, create big text
{'text': "blablablabla"}

Currently, I'm using POST requests to send the data, however I think it is against best-practices to use POST requests unless we are creating resources.

Now, you ask me: Why not just use GET requests?

Answer: Url length issues. Some parameters that I'm sending are 3000 chars long, which is way over the max url length in some browsers (eg. Edge 16 (2047 max length)).

I've had a look at this post, which is about a very similar topic. They recommend creating a file system that would work the following way:

1. Send POST request, create a file with text output named using uuid4() and return the file name.

2. Send GET Request with the file name, return the file content and delete the file.

3. If the file, is not acessed in a few minutes, delete it automaticaly.

I would like to know, what you guys think about this approach and if there is other good approach.

Thank you and I apologize if there is any grammar mistakes.

Answer 1

Using POST requests is perfectly fine. The POST request method is in a sense a catch-all for when no other method is appropriate. In particular, using POST is appropriate for doing some processing on your server, regardless of whether this causes resources to be created.

Your POST–redirect–GET approach sounds overly complicated for your use case. And complex code breeds bugs. So I wouldn't got that route unless you had a particular reason. One reason might be that you want to support caching of the output. By itself, a POST request is not cacheable or repeatable. In contrast, creating a resource that can be accessed via GET could allow multiple clients to access the same result, or to allow a client to access the result later without having to store it locally. But those are special requirements that you probably don't have.