.NET 11 Gives MemoryCache First-Class OpenTelemetry Metrics

The single most useful number for any read-heavy service is the cache hit ratio, and until now Microsoft.Extensions.Caching.Memory made you fish for it. .NET 11 Preview 4, released on June 2, 2026, fixes that: MemoryCache now emits OpenTelemetry metrics from a built-in meter, so hits, misses, evictions, and size land in your dashboards without a single line of custom plumbing.

What TrackStatistics Used to Cost You

TrackStatistics and GetCurrentStatistics() have existed since .NET 8, but they only handed you a snapshot object. To turn that into a time series you had to write a hosted service that polled the cache on a timer and republished the numbers through your own Meter:

// Pre-.NET 11: poll the snapshot yourself
public class CacheStatsReporter(IMemoryCache cache) : BackgroundService
{
    protected override async Task ExecuteAsync(CancellationToken ct)
    {
        while (!ct.IsCancellationRequested)
        {
            var stats = ((MemoryCache)cache).GetCurrentStatistics();
            // manually push stats.TotalHits, stats.TotalMisses, ...
            await Task.Delay(TimeSpan.FromSeconds(5), ct);
        }
    }
}

That works, but the cast is ugly, the polling interval is a guess, and every project reinvents the same boilerplate.

The Built-In Meter

Preview 4 adds a meter named Microsoft.Extensions.Caching.Memory with four observable instruments:

dotnet.cache.requests carries a cache.request.type tag valued hit or miss, which is exactly what you need to compute hit ratio in the dashboard rather than in the app. Every instrument also carries a cache.name tag, so multiple caches in one process stay distinct.

Wiring It Up

Two steps: turn on statistics and register the meter with OpenTelemetry.

builder.Services.AddMemoryCache(options =>
{
    options.TrackStatistics = true;
    options.Name = "catalog";
});

builder.Services.AddOpenTelemetry()
    .WithMetrics(metrics =>
    {
        metrics.AddMeter("Microsoft.Extensions.Caching.Memory");
    });

The instruments stay dormant until TrackStatistics is set, so there is no overhead if you never opt in. Give each cache a Name and the cache.name tag makes the catalog cache trivially separable from the session cache in Grafana or Azure Monitor.

The metrics slot in next to the native OpenTelemetry tracing ASP.NET Core picked up earlier in the .NET 11 cycle, which means a request trace and the cache behavior behind it now share the same pipeline. Grab .NET 11 Preview 4 and delete your cache-stats BackgroundService.