diff --git a/internal/caching/cache_space_rooms.go b/internal/caching/cache_space_rooms.go
new file mode 100644
index 00000000..71b81abc
--- /dev/null
+++ b/internal/caching/cache_space_rooms.go
@@ -0,0 +1,28 @@
+package caching
+
+import "github.com/matrix-org/gomatrixserverlib"
+
+const (
+	SpaceSummaryRoomsCacheName       = "space_summary_rooms"
+	SpaceSummaryRoomsCacheMaxEntries = 100
+	SpaceSummaryRoomsCacheMutable    = true
+)
+
+type SpaceSummaryRoomsCache interface {
+	GetSpaceSummary(roomID string) (r gomatrixserverlib.MSC2946SpacesResponse, ok bool)
+	StoreSpaceSummary(roomID string, r gomatrixserverlib.MSC2946SpacesResponse)
+}
+
+func (c Caches) GetSpaceSummary(roomID string) (r gomatrixserverlib.MSC2946SpacesResponse, ok bool) {
+	val, found := c.SpaceSummaryRooms.Get(roomID)
+	if found && val != nil {
+		if resp, ok := val.(gomatrixserverlib.MSC2946SpacesResponse); ok {
+			return resp, true
+		}
+	}
+	return r, false
+}
+
+func (c Caches) StoreSpaceSummary(roomID string, r gomatrixserverlib.MSC2946SpacesResponse) {
+	c.SpaceSummaryRooms.Set(roomID, r)
+}
diff --git a/internal/caching/caches.go b/internal/caching/caches.go
index e1642a66..39926d73 100644
--- a/internal/caching/caches.go
+++ b/internal/caching/caches.go
@@ -10,6 +10,7 @@ type Caches struct {
 	RoomServerRoomIDs  Cache // RoomServerNIDsCache
 	RoomInfos          Cache // RoomInfoCache
 	FederationEvents   Cache // FederationEventsCache
+	SpaceSummaryRooms  Cache // SpaceSummaryRoomsCache
 }
 
 // Cache is the interface that an implementation must satisfy.
diff --git a/internal/caching/impl_inmemorylru.go b/internal/caching/impl_inmemorylru.go
index ccb92852..7b21f136 100644
--- a/internal/caching/impl_inmemorylru.go
+++ b/internal/caching/impl_inmemorylru.go
@@ -55,9 +55,18 @@ func NewInMemoryLRUCache(enablePrometheus bool) (*Caches, error) {
 	if err != nil {
 		return nil, err
 	}
+	spaceRooms, err := NewInMemoryLRUCachePartition(
+		SpaceSummaryRoomsCacheName,
+		SpaceSummaryRoomsCacheMutable,
+		SpaceSummaryRoomsCacheMaxEntries,
+		enablePrometheus,
+	)
+	if err != nil {
+		return nil, err
+	}
 	go cacheCleaner(
 		roomVersions, serverKeys, roomServerRoomIDs,
-		roomInfos, federationEvents,
+		roomInfos, federationEvents, spaceRooms,
 	)
 	return &Caches{
 		RoomVersions:      roomVersions,
@@ -65,6 +74,7 @@ func NewInMemoryLRUCache(enablePrometheus bool) (*Caches, error) {
 		RoomServerRoomIDs: roomServerRoomIDs,
 		RoomInfos:         roomInfos,
 		FederationEvents:  federationEvents,
+		SpaceSummaryRooms: spaceRooms,
 	}, nil
 }
 
diff --git a/setup/mscs/msc2946/msc2946.go b/setup/mscs/msc2946/msc2946.go
index f53e7b24..7ab50c32 100644
--- a/setup/mscs/msc2946/msc2946.go
+++ b/setup/mscs/msc2946/msc2946.go
@@ -30,6 +30,7 @@ import (
 	"github.com/gorilla/mux"
 	"github.com/matrix-org/dendrite/clientapi/jsonerror"
 	fs "github.com/matrix-org/dendrite/federationapi/api"
+	"github.com/matrix-org/dendrite/internal/caching"
 	"github.com/matrix-org/dendrite/internal/httputil"
 	roomserver "github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/setup/base"
@@ -54,9 +55,9 @@ type MSC2946ClientResponse struct {
 // Enable this MSC
 func Enable(
 	base *base.BaseDendrite, rsAPI roomserver.RoomserverInternalAPI, userAPI userapi.UserInternalAPI,
-	fsAPI fs.FederationInternalAPI, keyRing gomatrixserverlib.JSONVerifier,
+	fsAPI fs.FederationInternalAPI, keyRing gomatrixserverlib.JSONVerifier, cache caching.SpaceSummaryRoomsCache,
 ) error {
-	clientAPI := httputil.MakeAuthAPI("spaces", userAPI, spacesHandler(rsAPI, fsAPI, base.Cfg.Global.ServerName))
+	clientAPI := httputil.MakeAuthAPI("spaces", userAPI, spacesHandler(rsAPI, fsAPI, cache, base.Cfg.Global.ServerName))
 	base.PublicClientAPIMux.Handle("/v1/rooms/{roomID}/hierarchy", clientAPI).Methods(http.MethodGet, http.MethodOptions)
 	base.PublicClientAPIMux.Handle("/unstable/org.matrix.msc2946/rooms/{roomID}/hierarchy", clientAPI).Methods(http.MethodGet, http.MethodOptions)
 
@@ -74,7 +75,7 @@ func Enable(
 				return util.ErrorResponse(err)
 			}
 			roomID := params["roomID"]
-			return federatedSpacesHandler(req.Context(), fedReq, roomID, rsAPI, fsAPI, base.Cfg.Global.ServerName)
+			return federatedSpacesHandler(req.Context(), fedReq, roomID, cache, rsAPI, fsAPI, base.Cfg.Global.ServerName)
 		},
 	)
 	base.PublicFederationAPIMux.Handle("/unstable/org.matrix.msc2946/hierarchy/{roomID}", fedAPI).Methods(http.MethodGet)
@@ -84,6 +85,7 @@ func Enable(
 
 func federatedSpacesHandler(
 	ctx context.Context, fedReq *gomatrixserverlib.FederationRequest, roomID string,
+	cache caching.SpaceSummaryRoomsCache,
 	rsAPI roomserver.RoomserverInternalAPI, fsAPI fs.FederationInternalAPI,
 	thisServer gomatrixserverlib.ServerName,
 ) util.JSONResponse {
@@ -100,6 +102,7 @@ func federatedSpacesHandler(
 		serverName:    fedReq.Origin(),
 		thisServer:    thisServer,
 		ctx:           ctx,
+		cache:         cache,
 		suggestedOnly: u.Query().Get("suggested_only") == "true",
 		limit:         1000,
 		// The main difference is that it does not recurse into spaces and does not support pagination.
@@ -115,7 +118,9 @@ func federatedSpacesHandler(
 }
 
 func spacesHandler(
-	rsAPI roomserver.RoomserverInternalAPI, fsAPI fs.FederationInternalAPI,
+	rsAPI roomserver.RoomserverInternalAPI,
+	fsAPI fs.FederationInternalAPI,
+	cache caching.SpaceSummaryRoomsCache,
 	thisServer gomatrixserverlib.ServerName,
 ) func(*http.Request, *userapi.Device) util.JSONResponse {
 	// declared outside the returned handler so it persists between calls
@@ -138,6 +143,7 @@ func spacesHandler(
 			caller:          device,
 			thisServer:      thisServer,
 			ctx:             req.Context(),
+			cache:           cache,
 
 			rsAPI:           rsAPI,
 			fsAPI:           fsAPI,
@@ -160,6 +166,7 @@ type walker struct {
 	rsAPI           roomserver.RoomserverInternalAPI
 	fsAPI           fs.FederationInternalAPI
 	ctx             context.Context
+	cache           caching.SpaceSummaryRoomsCache
 	suggestedOnly   bool
 	limit           int
 	maxDepth        int
@@ -169,13 +176,6 @@ type walker struct {
 	mu              sync.Mutex
 }
 
-func (w *walker) callerID() string {
-	if w.caller != nil {
-		return w.caller.UserID + "|" + w.caller.ID
-	}
-	return string(w.serverName)
-}
-
 func (w *walker) newPaginationCache() (string, paginationInfo) {
 	p := paginationInfo{
 		processed: make(set),
@@ -414,7 +414,12 @@ func (w *walker) federatedRoomInfo(roomID string, vias []string) (*gomatrixserve
 	if w.caller == nil {
 		return nil, nil
 	}
-	util.GetLogger(w.ctx).Infof("Querying %s via %+v", roomID, vias)
+	resp, ok := w.cache.GetSpaceSummary(roomID)
+	if ok {
+		util.GetLogger(w.ctx).Debugf("Returning cached response for %s", roomID)
+		return &resp, nil
+	}
+	util.GetLogger(w.ctx).Debugf("Querying %s via %+v", roomID, vias)
 	ctx := context.Background()
 	// query more of the spaces graph using these servers
 	for _, serverName := range vias {
@@ -437,6 +442,7 @@ func (w *walker) federatedRoomInfo(roomID string, vias []string) (*gomatrixserve
 			}
 			res.Children[i] = child
 		}
+		w.cache.StoreSpaceSummary(roomID, res)
 
 		return &res, nil
 	}
diff --git a/setup/mscs/mscs.go b/setup/mscs/mscs.go
index 10df6a15..35b7bba3 100644
--- a/setup/mscs/mscs.go
+++ b/setup/mscs/mscs.go
@@ -42,7 +42,7 @@ func EnableMSC(base *base.BaseDendrite, monolith *setup.Monolith, msc string) er
 	case "msc2836":
 		return msc2836.Enable(base, monolith.RoomserverAPI, monolith.FederationAPI, monolith.UserAPI, monolith.KeyRing)
 	case "msc2946":
-		return msc2946.Enable(base, monolith.RoomserverAPI, monolith.UserAPI, monolith.FederationAPI, monolith.KeyRing)
+		return msc2946.Enable(base, monolith.RoomserverAPI, monolith.UserAPI, monolith.FederationAPI, monolith.KeyRing, base.Caches)
 	case "msc2444": // enabled inside federationapi
 	case "msc2753": // enabled inside clientapi
 	default: