diff --git a/src/azul/plugins/__init__.py b/src/azul/plugins/__init__.py
index 893499fb2..2fab31a4e 100644
--- a/src/azul/plugins/__init__.py
+++ b/src/azul/plugins/__init__.py
@@ -413,13 +413,12 @@ def special_fields(self) -> SpecialFields:
 
     @property
     @abstractmethod
-    def implicit_hub_type(self) -> str:
+    def hot_entity_types(self) -> AbstractSet[str]:
         """
-        The type of entities that do not explicitly track their hubs in replica
+        The types of entities that do not explicitly track their hubs in replica
         documents in order to avoid a large list of hub references in the
         replica document, and to avoid contention when updating that list during
-        indexing. Note that this is not a type of hub entities, but rather the
-        type of replica entities that have implicit hubs.
+        indexing.
         """
         raise NotImplementedError
 
diff --git a/src/azul/plugins/metadata/anvil/__init__.py b/src/azul/plugins/metadata/anvil/__init__.py
index b3fe44532..3290dd57a 100644
--- a/src/azul/plugins/metadata/anvil/__init__.py
+++ b/src/azul/plugins/metadata/anvil/__init__.py
@@ -5,6 +5,7 @@
     itemgetter,
 )
 from typing import (
+    AbstractSet,
     Iterable,
     Sequence,
 )
@@ -249,8 +250,8 @@ def special_fields(self) -> SpecialFields:
                              bundle_version='bundle_version')
 
     @property
-    def implicit_hub_type(self) -> str:
-        return 'datasets'
+    def hot_entity_types(self) -> AbstractSet[str]:
+        return {'datasets'}
 
     @property
     def facets(self) -> Sequence[str]:
diff --git a/src/azul/plugins/metadata/hca/__init__.py b/src/azul/plugins/metadata/hca/__init__.py
index 0286a2b48..85f4ce1c7 100644
--- a/src/azul/plugins/metadata/hca/__init__.py
+++ b/src/azul/plugins/metadata/hca/__init__.py
@@ -1,4 +1,5 @@
 from typing import (
+    AbstractSet,
     Iterable,
     Sequence,
     TYPE_CHECKING,
@@ -285,8 +286,8 @@ def special_fields(self) -> SpecialFields:
                              bundle_version='bundleVersion')
 
     @property
-    def implicit_hub_type(self) -> str:
-        return 'projects'
+    def hot_entity_types(self) -> AbstractSet[str]:
+        return {'projects'}
 
     @property
     def facets(self) -> Sequence[str]:
diff --git a/src/azul/service/manifest_service.py b/src/azul/service/manifest_service.py
index dc3ad7ba0..5739c0381 100644
--- a/src/azul/service/manifest_service.py
+++ b/src/azul/service/manifest_service.py
@@ -48,6 +48,7 @@
 )
 import time
 from typing import (
+    AbstractSet,
     IO,
     Protocol,
     Self,
@@ -1992,12 +1993,15 @@ def included_fields(self) -> list[FieldPath]:
         # "keys" used for the join.
         return [
             ('entity_id',),
-            ('contents', self.implicit_hub_type, 'document_id')
+            *(
+                ('contents', entity_type, 'document_id')
+                for entity_type in self.hot_entity_types
+            )
         ]
 
     @property
-    def implicit_hub_type(self) -> str:
-        return self.service.metadata_plugin(self.catalog).implicit_hub_type
+    def hot_entity_types(self) -> AbstractSet[str]:
+        return self.service.metadata_plugin(self.catalog).hot_entity_types
 
     @attrs.frozen(kw_only=True)
     class ReplicaKeys:
@@ -2011,14 +2015,17 @@ class ReplicaKeys:
         or the replica's entity ID.
         """
         hub_id: str
-        replica_id: str
+        replica_ids: list[str]
 
     def _replica_keys(self) -> Iterable[ReplicaKeys]:
-        hub_type = self.implicit_hub_type
         request = self._create_request()
         for hit in request.scan():
             yield self.ReplicaKeys(hub_id=hit['entity_id'],
-                                   replica_id=one(one(hit['contents'][hub_type])['document_id']))
+                                   replica_ids=[
+                                       document_id
+                                       for entity_type in self.hot_entity_types
+                                       for document_id in hit['contents'][entity_type]['document_id']
+                                   ])
 
     def _all_replicas(self) -> Iterable[JSON]:
         emitted_replica_ids = set()
@@ -2053,7 +2060,7 @@ def _join_replicas(self, keys: Iterable[ReplicaKeys]) -> Iterable[Hit]:
         hub_ids, replica_ids = set(), set()
         for key in keys:
             hub_ids.add(key.hub_id)
-            replica_ids.add(key.replica_id)
+            replica_ids.update(key.replica_ids)
         request = request.query(Q('bool', should=[
             {'terms': {'hub_ids.keyword': list(hub_ids)}},
             {'terms': {'entity_id.keyword': list(replica_ids)}}