Output Caching vs In-Memory Cache

Question

Microsoft introduced Output Caching with .NET 7.

As far as I understood, Output Caching caches the HTTP response while In-Memory Cache stores data in the memory of the server.

I don't feel sure about which of the two I should use from now on. Is there a general recommendation? In case it depends on the scenario, can anybody list some examples / scenarios where it makes more sense to use Output Caching instead of In-Memory Cache and vice versa?

I'm aware that there are also Distributed Caching and Response Caching, but they're out of scope for this question.

Answer 1

Output cache is created specifically for caching of HTTP responses and integrates with ASP.NET Core request handling pipeline, i.e. it will cache the whole result of the endpoint invocation, while memory cache allows you to cache anything. For example lets imagine you have an endpoint:

app.MapGet("/api/something/{id}", (id) =>
{
    var item = GetSomething(id);
    var anotherItem = GetSomethingElse();
    return Combine(item, anotherItem);
});

The output cache will cache the whole response of the handler (varying by id ideally =). It can be desired behavior, but it can be not, for example you may want to cache only item and anotherItem always should be "fresh" - then you can use in-memory cache to cache only the item and compute everything else on every invocation.