No, the author is not confusing them. It’s everyone else that has been confused insofar as they use “REST” to describe APIs that are not actually REST. True REST is a way of architecting networked applications according to a set of constraints, as defined by Roy Fielding in his original dissertation. Here’s an excerpt that sums it up:

In order to obtain a uniform interface, multiple architectural constraints are needed to guide the behavior of components. REST is defined by four interface constraints: identification of resources; manipulation of resources through representations; self-descriptive messages; and, hypermedia as the engine of application state.

Many “REST” APIs do not adhere to these constraints, especially self-descriptive messages and hypermedia as the engine of application state (also known as HATEOAS). Note that this says nothing about HTML: HTML is but one representation of hypermedia, but far from the only one. Hypermedia is something that allows discovery of additional, related resources by way of links between resources. There are a number of ways of doing this, such as RFC 8288 Link Headers or embedding links within one of a resource’s representations (such as a JSON representation).

It’s a much larger topic than I can fully explain here, but I highly recommend reading Roy Fielding’s dissertation, especially Chapter 5 which talks about REST and what it is.

I also highly recommend this blog post from Google Cloud’s engineering team, which talks about why you should use links instead of keys to represent relationships in API design: https://cloud.google.com/blog/products/application-development/api-design-why-you-should-use-links-not-keys-to-represent-relationships-in-apis.

That’s what Open Telemetry is for, honestly, specifically tracing. I’m in the process of adding tracing for all of our web handlers, http client calls, database transactions/individual queries, and asynchronous jobs. Should give us a pretty good view into the performance of the system, and allow us to monitor for things like performance regressions without any dedicated profiling needed (though we certainly could add additional profiling information through Otel down the road). Since I know you’re a Haskeller (recognize your handle), the hs-opentelemetryecosystem is quite solid and has integrations with a lot of libraries in the wider ecosystem, like wai, persistent, postgresql-simple, conduit, and a bunch more. I haven’t needed to write too much of our own instrumentation, aside from our job system since that’s a bespoke system.