You may not be able to present cacheable data to your end-users, but you can still utilize caching for internal consumers (such as application-layer services consuming data from enterprise-layer services).

Or, if you have a CDN, you could cache closer to the end-user (assuming you have the necessary controls on your CDN to meet regulatory [and common-sense] requirements).

Yep, caching in generally totally makes sense where possible and agree re: services and CDNs.

But end-to-end cacheability at the HTTP layer, part of the original rationale behind the REST API design style, does not make sense for most APIs anymore in 2018.

> But end-to-end cacheability at the HTTP layer, part of the original rationale behind the REST API design style, does not make sense for most APIs anymore in 2018.

Why not? What were the relevant changes between the 90s and 2018?

* Most APIs are authenticated.

* HTTPS has broken intermediate caches.

* Most responses are personalised or highly dynamic.

* Many responses contain PII or sensitive information and should not be cached.

* Many requests are rate-limited, billed or metered.

Observation: people go out of their way to cache static resources but tend to disable caching entirely on their JSON APIs.

I do have some bias; recovering pentester who rarely worked with APIs that served the same response to all users.

There are still many use-cases for HTTP caches within internal infrastructure—such as between microservices.