Azure Cosmos DB

dotnet add package ActionCache.AzureCosmos

builder.Services.AddActionCache(options =>
{
    options.UseAzureCosmosCache(cosmos =>
    {
        cosmos.DatabaseId = "MyDatabase";
        cosmos.ConnectionString = configuration.GetValue<string>("CosmosDb:ConnectionString");
    });
});

Both DatabaseId and ConnectionString are required.

Provisioning

The only thing to create in Azure is the Cosmos DB account. The database and container are created on first use if they do not already exist, so there is no setup script to run.

Initialization is lazy — it happens on the first cache operation rather than at startup, so an application does not fail to start because Cosmos is unreachable.

Storage shape

Each entry is a document holding the key, the namespace, the serialized value, and its expiration as both an absolute timestamp and a Cosmos ttl. Expiry is enforced by the container’s TTL rather than by a background sweep.

The serialized value is a JSON string inside that document, so a cached body is escaped once as JSON and again as the document’s field.

Locking

None needed — operations are atomic.

Cosmos does not supply a distributed lock, so it cannot back UseDistributedSingleFlight(). Register Redis or SQL Server alongside it if you need cross-instance coalescing.

Cancellation

The Cosmos backend forwards the CancellationToken to the SDK.