diff --git a/dev/restate/services.proto b/dev/restate/services.proto
index bed0a86..4cd1380 100644
--- a/dev/restate/services.proto
+++ b/dev/restate/services.proto
@@ -25,19 +25,27 @@ service Ingress {
   // Invoke a service and don't wait for the response.
   // It is guaranteed that the service will be invoked after this method returns.
   rpc Invoke(InvokeRequest) returns (InvokeResponse);
+
+  // Invoke a service in an idempotent fashion.
+  // If already invoked, this will return the cached response.
+  // The response will be cleaned up after a retention period.
+  rpc IdempotentInvoke(IdempotentInvokeRequest) returns (IdempotentInvokeResponse);
 }
 
 message InvokeRequest {
   // Fully qualified name of the service, e.g. `counter.Counter`
   string service = 1;
+
   // Method name of the service to invoke, e.g. `Add`
   string method = 2;
+
   // Argument of the invocation.
-  // When executing requests to the ingress using Protobuf,
-  // this field must contain the serialized Protobuf matching the argument type of the target method.
-  // When executing requests to the ingress using JSON,
-  // this field must contain the JSON object representing the argument type of the target method.
-  bytes argument = 3;
+  // You can pass the invocation argument either as protobuf or as JSON.
+  // In case of JSON, the argument will be automatically transcoded to protobuf.
+  oneof argument {
+    bytes pb = 3;
+    google.protobuf.Struct json = 4 [json_name = "argument"];
+  }
 }
 
 message InvokeResponse {
@@ -46,6 +54,44 @@ message InvokeResponse {
   string id = 1;
 }
 
+message IdempotentInvokeRequest {
+  // Idempotency id.
+  string idempotency_id = 1;
+
+  // Fully qualified name of the service, e.g. `counter.Counter`
+  string service = 2;
+
+  // Method name of the service to invoke, e.g. `Add`
+  string method = 3;
+
+  // Argument of the invocation.
+  // You can pass the invocation argument either as protobuf or as JSON.
+  // In case of JSON, the argument will be automatically transcoded to protobuf.
+  oneof argument {
+    bytes pb = 4;
+    google.protobuf.Struct json = 5 [json_name = "argument"];
+  }
+
+  // Retention period for the response in seconds.
+  // After the invocation completes, the response will be persisted for the given duration.
+  // Afterwards, the system will cleanup the response and treats any subsequent invocation with same id as new.
+  //
+  // If not set, 30 minutes will be used as retention period.
+  uint32 retention_period_sec = 6;
+}
+
+message IdempotentInvokeResponse {
+  // Invocation response.
+  // The response will be provided in the same format used for the request.
+  oneof response {
+    bytes pb = 1;
+    google.protobuf.Struct json = 2 [json_name = "response"];
+  }
+
+  // Timestamp of the response expiry time in RFC3339.
+  string expiry_time = 3;
+}
+
 service Awakeables {
   // Resolve an Awakeable with a result value.
   rpc Resolve(ResolveAwakeableRequest) returns (google.protobuf.Empty);