diff --git a/federationsender/api/query.go b/federationsender/api/query.go
new file mode 100644
index 00000000..ebc6e833
--- /dev/null
+++ b/federationsender/api/query.go
@@ -0,0 +1,98 @@
+package api
+
+import (
+	"context"
+	"net/http"
+
+	commonHTTP "github.com/matrix-org/dendrite/common/http"
+	"github.com/matrix-org/gomatrixserverlib"
+
+	"github.com/matrix-org/dendrite/federationsender/types"
+	"github.com/opentracing/opentracing-go"
+)
+
+// QueryJoinedHostsInRoomRequest is a request to QueryJoinedHostsInRoom
+type QueryJoinedHostsInRoomRequest struct {
+	RoomID string `json:"room_id"`
+}
+
+// QueryJoinedHostsInRoomResponse is a response to QueryJoinedHostsInRoom
+type QueryJoinedHostsInRoomResponse struct {
+	JoinedHosts []types.JoinedHost `json:"joined_hosts"`
+}
+
+// QueryJoinedHostServerNamesRequest is a request to QueryJoinedHostServerNames
+type QueryJoinedHostServerNamesInRoomRequest struct {
+	RoomID string `json:"room_id"`
+}
+
+// QueryJoinedHostServerNamesResponse is a response to QueryJoinedHostServerNames
+type QueryJoinedHostServerNamesInRoomResponse struct {
+	ServerNames []gomatrixserverlib.ServerName `json:"server_names"`
+}
+
+// FederationSenderQueryAPI is used to query information from the federation sender.
+type FederationSenderQueryAPI interface {
+	// Query the joined hosts and the membership events accounting for their participation in a room.
+	// Note that if a server has multiple users in the room, it will have multiple entries in the returned slice.
+	// See `QueryJoinedHostServerNamesInRoom` for a de-duplicated version.
+	QueryJoinedHostsInRoom(
+		ctx context.Context,
+		request *QueryJoinedHostsInRoomRequest,
+		response *QueryJoinedHostsInRoomResponse,
+	) error
+	// Query the server names of the joined hosts in a room.
+	// Unlike QueryJoinedHostsInRoom, this function returns a de-duplicated slice
+	// containing only the server names (without information for membership events).
+	QueryJoinedHostServerNamesInRoom(
+		ctx context.Context,
+		request *QueryJoinedHostServerNamesInRoomRequest,
+		response *QueryJoinedHostServerNamesInRoomResponse,
+	) error
+}
+
+// FederationSenderQueryJoinedHostsInRoomPath is the HTTP path for the QueryJoinedHostsInRoom API.
+const FederationSenderQueryJoinedHostsInRoomPath = "/api/federationsender/queryJoinedHostsInRoom"
+
+// FederationSenderQueryJoinedHostServerNamesInRoomPath is the HTTP path for the QueryJoinedHostServerNamesInRoom API.
+const FederationSenderQueryJoinedHostServerNamesInRoomPath = "/api/federationsender/queryJoinedHostServerNamesInRoom"
+
+// NewFederationSenderQueryAPIHTTP creates a FederationSenderQueryAPI implemented by talking to a HTTP POST API.
+// If httpClient is nil then it uses the http.DefaultClient
+func NewFederationSenderQueryAPIHTTP(federationSenderURL string, httpClient *http.Client) FederationSenderQueryAPI {
+	if httpClient == nil {
+		httpClient = http.DefaultClient
+	}
+	return &httpFederationSenderQueryAPI{federationSenderURL, httpClient}
+}
+
+type httpFederationSenderQueryAPI struct {
+	federationSenderURL string
+	httpClient          *http.Client
+}
+
+// QueryJoinedHostsInRoom implements FederationSenderQueryAPI
+func (h *httpFederationSenderQueryAPI) QueryJoinedHostsInRoom(
+	ctx context.Context,
+	request *QueryJoinedHostsInRoomRequest,
+	response *QueryJoinedHostsInRoomResponse,
+) error {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "QueryJoinedHostsInRoom")
+	defer span.Finish()
+
+	apiURL := h.federationSenderURL + FederationSenderQueryJoinedHostsInRoomPath
+	return commonHTTP.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+}
+
+// QueryJoinedHostServerNamesInRoom implements FederationSenderQueryAPI
+func (h *httpFederationSenderQueryAPI) QueryJoinedHostServerNamesInRoom(
+	ctx context.Context,
+	request *QueryJoinedHostServerNamesInRoomRequest,
+	response *QueryJoinedHostServerNamesInRoomResponse,
+) error {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "QueryJoinedHostServerNamesInRoom")
+	defer span.Finish()
+
+	apiURL := h.federationSenderURL + FederationSenderQueryJoinedHostServerNamesInRoomPath
+	return commonHTTP.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+}
diff --git a/federationsender/query/query.go b/federationsender/query/query.go
new file mode 100644
index 00000000..ec924286
--- /dev/null
+++ b/federationsender/query/query.go
@@ -0,0 +1,55 @@
+package query
+
+import (
+	"context"
+
+	"github.com/matrix-org/dendrite/federationsender/api"
+	"github.com/matrix-org/dendrite/federationsender/types"
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+// FederationSenderQueryDatabase has the APIs needed to implement the query API.
+type FederationSenderQueryDatabase interface {
+	GetJoinedHosts(
+		ctx context.Context, roomID string,
+	) ([]types.JoinedHost, error)
+}
+
+// FederationSenderQueryAPI is an implementation of api.FederationSenderQueryAPI
+type FederationSenderQueryAPI struct {
+	DB FederationSenderQueryDatabase
+}
+
+// QueryJoinedHostsInRoom implements api.FederationSenderQueryAPI
+func (f *FederationSenderQueryAPI) QueryJoinedHostsInRoom(
+	ctx context.Context,
+	request *api.QueryJoinedHostsInRoomRequest,
+	response *api.QueryJoinedHostsInRoomResponse,
+) (err error) {
+	response.JoinedHosts, err = f.DB.GetJoinedHosts(ctx, request.RoomID)
+	return
+}
+
+// QueryJoinedHostServerNamesInRoom implements api.FederationSenderQueryAPI
+func (f *FederationSenderQueryAPI) QueryJoinedHostServerNamesInRoom(
+	ctx context.Context,
+	request *api.QueryJoinedHostServerNamesInRoomRequest,
+	response *api.QueryJoinedHostServerNamesInRoomResponse,
+) (err error) {
+	joinedHosts, err := f.DB.GetJoinedHosts(ctx, request.RoomID)
+	if err != nil {
+		return
+	}
+
+	serverNamesSet := make(map[gomatrixserverlib.ServerName]bool, len(joinedHosts))
+	for _, host := range joinedHosts {
+		serverNamesSet[host.ServerName] = true
+	}
+
+	response.ServerNames = make([]gomatrixserverlib.ServerName, 0, len(serverNamesSet))
+	for name := range serverNamesSet {
+		response.ServerNames = append(response.ServerNames, name)
+	}
+
+	return
+}