Provider Capabilities

Provider Capabilities

Event-store capabilities are exposed as a provider-neutral, queryable contract so applications and Admin tooling can determine actual guarantees instead of inferring them from a provider name.

Discovery

Resolve IEventStoreCapabilitiesProvider from dependency injection:

public sealed class StoreHealth(IEventStoreCapabilitiesProvider capabilitiesProvider)
{
  public void Report()
  {
    var capabilities = capabilitiesProvider.GetCapabilities();
    var guarantee = capabilities.TransactionGuarantee;
    var preservesMetadata = capabilities.PreservedMetadata;
  }
}

Capability discovery never constructs a store or probes live storage; it only reads what was registered. IEventStoreCapabilitiesProvider is always resolvable after AddEventSourcing() and reports the conservative EventStoreCapabilities.Default until a provider registers its capabilities.

What is exposed

Member	Meaning
TransactionGuarantee	EventStoreTransactionGuarantee.Atomic or .BestEffort (the same abstraction used by transaction options).
SupportsEventStreams	Whether the provider persists an append-only event stream.
SupportsSnapshots	Whether the provider stores aggregate snapshots (replay cache or query store).
SnapshotSchemaVersioning	None, SingleVersion (legacy single-shape layout), or Versioned (honors [SnapshotSchemaVersion]).
PreservedMetadata	Flags for which event metadata fields are persisted: SchemaVersion, CorrelationId, CausationId, UserId, IdempotencyId, AggregateVersion, When.
SupportsQueries	Whether a queryable snapshot store is available through IQueryableEventStore.
SupportsIdempotencyMarkers	Whether saves deduplicate on an idempotency marker.
Concurrency	Optimistic (conflicts rejected) or LastWriterWins.
OperationalLimitations	Stable limitation identifiers, for example non-persistent (InMemory) and no-event-stream (Cosmos DB).

Registration

Built-in providers register their truthful capabilities from their Add*EventStore extension methods. Multiple registrations for the same provider are merged into the union of what is actually available (for example SQL Server event store + snapshot query store report atomic transactions, event streams, snapshots, and queries).

Custom providers register their own capabilities explicitly:

services.AddEventStoreCapabilities(new EventStoreCapabilities(
  EventStoreTransactionGuarantee.BestEffort,
  SupportsEventStreams: true,
  SupportsSnapshots: false,
  SnapshotSchemaVersioning: SnapshotSchemaSupport.None,
  PreservedMetadata: PreservedEventMetadata.All,
  SupportsQueries: false,
  SupportsIdempotencyMarkers: false,
  Concurrency: ConcurrencyGuarantee.Optimistic,
  OperationalLimitations: []
));

Providers that register nothing are reported with EventStoreCapabilities.Default: best-effort transactions, no streams, no snapshots, no queries, no idempotency, and LastWriterWins concurrency. A provider is never assumed to offer stronger behavior than it implements.

Built-in capabilities

The values below are asserted by the Capabilities.UnitTests contract suite so documentation and implementation cannot drift apart.

Provider	Transactions	Event streams	Snapshots	Snapshot versions	Metadata	Queries	Idempotency	Concurrency	Transactional outbox
InMemory event store	BestEffort	Yes	No	None	All	No	Yes	Optimistic	No
InMemory snapshot store	BestEffort	Yes	Yes	SingleVersion	All	Yes	Yes	Optimistic	No
SQL Server event store	Atomic	Yes	Yes	Versioned	All	No	Yes	Optimistic	Yes
SQL Server snapshot query store	Atomic	No	Yes	SingleVersion	None	Yes	No	Optimistic	No
PostgreSQL event store	Atomic	Yes	Yes	Versioned	All	No	Yes	Optimistic	Yes
PostgreSQL snapshot query store	Atomic	No	Yes	SingleVersion	None	Yes	No	Optimistic	No
Azure Storage	BestEffort	Yes	Yes	Versioned	All	No	Yes	Optimistic	No
MongoDB event store	BestEffort	Yes	Yes	Versioned	All	No	Yes	Optimistic	No
MongoDB snapshot query store	BestEffort	No	Yes	SingleVersion	None	Yes	No	Optimistic	No
Cosmos DB snapshot query store	BestEffort	No	Yes	SingleVersion	None	Yes	No	Optimistic	No

The Provider Feature Matrix summarizes the same facts for package selection.