Comment by habitue | Hacker News Reader

Comment by habitue | Hacker News Reader

Differences between files and REST apis:

- files get persisted to disk by default. Usually we don't save every rest result to disk (though obviously, you could)

- files tend not to be processed at request time, but rather the directory acts as a queue. Usually with rest, we try to process things at request time until stuff gets too slow. Files always decouple

- multiple transports are the norm: SFTP, SMTP, etc. doesn't matter since it's not going to be processed at request time, but async. Think of "dropping it into a directory" as stripping off the transport layer the same way your web framework and reverse proxy abstract away http 2/3 for you.

- formats: much more variety than json everything. Back in the day, people liked to write custom parsers for everything. Nowadays, we like to let json be the bytes to in-memory data structure, and programmers recurse over that structure rather than spending their time ensuring their parser isn't ambiguous

Thanks for sharing habitue

It's true that REST APIs operate under the assumption of processing at request time, while not the case with files. That's what makes Bank REST APIs so tricky - processing doesn't ever actually occur at request time.

There are so many crazy formats that are supported. Simpler is better imo

> That's what makes Bank REST APIs so tricky - processing doesn't ever actually occur at request time.

HTTP has provisions to enable async semantics between the client and the server. I would always advocate for teams to return 202 Accepted responses with a Location header containing the absolute or relative path to an endpoint that can be interrogated for status of the underlying async operation. This can work fine for lower-scale services (or even higher scale services with rate limits enforced at gateway). You POST'd a payment. You get 202 Accepted with some Location value like (simplified) `/payments/<identifier>` for which GET can be used to retrieve current status (e.g. pending, failed, committed, etc).

If a polling model is not desirable you can also use webhooks and inform the caller whenever a given task is finished.

Both of these strategies work fairly well in practice in my experience. However, I Must agree that simply dropping a big file off at an sFTP share and moving on with life is certainly "easier" from the client perspective. But...do you then roll your own mechanism for checking status? Why not just use HTTP semantics that exist already?

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