Output caching in ASP.NET core

Output caching can be used on your endpoints so that if the same request comes into your endpoint within an “cache expiry” time then the endpoint will not get called and the stored/cached response from a previous call will be returned.

To make that clearer the endpoint’s method will NOT be called, the response is cached and hence returned via the ASP.NET middleware.

This is particularly useful for static or semi-static context.

Out of the box, the OutputCache can handle caching for different query parameters and routes can be easily set up to handle caching.

I’m going to setup the output cache to use Redis

builder.AddRedisOutputCache("cache");

builder.Services.AddOutputCache(options =>
{
    options.AddPolicy("ShortCache", builder => builder.Expire(TimeSpan.FromSeconds(10)));
});

Now from a minimal API endpoint we can apply output caching using CacheOutput as below 

app.MapGet("/cached/{id}", (int id) => new
    {
        Message = $"Output Cache {id}",
        Timestamp = DateTime.UtcNow
    })
    .CacheOutput(c => c.VaryByValue(
        ctx => new KeyValuePair<string, string>("id", ctx.Request.RouteValues["id"]?.ToString() ?? string.Empty)));

Each unique id gets its own cached response.

The endpoint is only executed once per id within the cache duration.
– The VaryByValue method lets you define custom cache keys based on route values, headers, or query strings.
– Without this, /cache/1 and /cache/2 might share a cache entry or overwrite each other depending on the default key behavior.

app.MapGet("/cached-query", (int id) => new
    {
        Message = $"Output Cache {id}",
        Timestamp = DateTime.UtcNow
    })
    .CacheOutput();

app.UseOutputCache();