diff --git a/grpc/lookup/v1/rls.proto b/grpc/lookup/v1/rls.proto
index bf399a03..d204d8ea 100644
--- a/grpc/lookup/v1/rls.proto
+++ b/grpc/lookup/v1/rls.proto
@@ -24,10 +24,12 @@ option java_outer_classname = "RlsProto";
 message RouteLookupRequest {
   // Full host name of the target server, e.g. firestore.googleapis.com.
   // Only set for gRPC requests; HTTP requests must use key_map explicitly.
-  string server = 1;
+  // Deprecated in favor of setting key_map keys with GrpcKeyBuilder.extra_keys.
+  string server = 1 [deprecated = true];
   // Full path of the request, i.e. "/service/method".
   // Only set for gRPC requests; HTTP requests must use key_map explicitly.
-  string path = 2;
+  // Deprecated in favor of setting key_map keys with GrpcKeyBuilder.extra_keys.
+  string path = 2 [deprecated = true];
   // Target type allows the client to specify what kind of target format it
   // would like from RLS to allow it to find the regional server, e.g. "grpc".
   string target_type = 3;
diff --git a/grpc/lookup/v1/rls_config.proto b/grpc/lookup/v1/rls_config.proto
index f2ed78d6..db99a894 100644
--- a/grpc/lookup/v1/rls_config.proto
+++ b/grpc/lookup/v1/rls_config.proto
@@ -29,6 +29,9 @@ option java_outer_classname = "RlsConfigProto";
 // present for the keybuilder to match.
 message NameMatcher {
   // The name that will be used in the RLS key_map to refer to this value.
+  // If required_match is true, you may omit this field or set it to an empty
+  // string, in which case the matcher will require a match, but won't update
+  // the key_map.
   string key = 1;
 
   // Ordered list of names (headers or query parameter names) that can supply
@@ -52,10 +55,29 @@ message GrpcKeyBuilder {
   }
   repeated Name names = 1;
 
+  // If you wish to include the host, service, or method names as keys in the
+  // generated RouteLookupRequest, specify key names to use in the extra_keys
+  // submessage. If a key name is empty, no key will be set for that value.
+  // If this submessage is specified, the normal host/path fields will be left
+  // unset in the RouteLookupRequest. We are deprecating host/path in the
+  // RouteLookupRequest, so services should migrate to the ExtraKeys approach.
+  message ExtraKeys {
+    string host = 1;
+    string service = 2;
+    string method = 3;
+  }
+  ExtraKeys extra_keys = 3;
+
   // Extract keys from all listed headers.
   // For gRPC, it is an error to specify "required_match" on the NameMatcher
   // protos.
   repeated NameMatcher headers = 2;
+
+  // You can optionally set one or more specific key/value pairs to be added to
+  // the key_map.  This can be useful to identify which builder built the key,
+  // for example if you are suppressing the actual method, but need to
+  // separately cache and request all the matched methods.
+  map<string, string> constant_keys = 4;
 }
 
 // An HttpKeyBuilder applies to a given HTTP URL and headers.
@@ -131,6 +153,12 @@ message HttpKeyBuilder {
   // to match.  If a given header appears multiple times in the request we will
   // report it as a comma-separated string, in standard HTTP fashion.
   repeated NameMatcher headers = 4;
+
+  // You can optionally set one or more specific key/value pairs to be added to
+  // the key_map.  This can be useful to identify which builder built the key,
+  // for example if you are suppressing a lot of information from the URL, but
+  // need to separately cache and request URLs with that content.
+  map<string, string> constant_keys = 5;
 }
 
 message RouteLookupConfig {