diff --git a/back/store.go b/back/store.go
index e717028..b5f9571 100644
--- a/back/store.go
+++ b/back/store.go
@@ -90,20 +90,23 @@ const schema = `
 	);
 
 	CREATE TABLE response (
-		id TEXT NOT NULL PRIMARY KEY,
+		id TEXT NOT NULL,
 		event_id TEXT NOT NULL,
 		guest_name TEXT NOT NULL,
 
+		PRIMARY KEY (id, event_id),
 		FOREIGN KEY (event_id) REFERENCES event(id)
 	);
 
 	CREATE TABLE response_time (
+		event_id TEXT NOT NULL,
 		response_id TEXT NOT NULL,
 		date DATE NOT NULL,
 		time INTEGER NOT NULL,
 
 		CHECK (0 <= time < 24),
-		UNIQUE (response_id, date, time)
+		UNIQUE (response_id, date, time),
+		FOREIGN KEY(event_id, response_id) REFERENCES response(event_id, id)
 	);
 	
 	CREATE TRIGGER enforce_valid_response_dates
@@ -300,8 +303,7 @@ func (s *Store) GetEventResponseSummary(ctx context.Context, query GetEventRespo
 	result.PerHourCounts = make(map[date.Date]map[int]int)
 	const perHourCountQuery = `
 		SELECT date, time, COUNT(*)
-		FROM response
-		JOIN response_time ON response.id = response_time.response_id
+		FROM response_time
 		WHERE event_id = ?
 		GROUP BY date, time;`
 	err = sqlitex.Exec(conn, perHourCountQuery,
@@ -344,16 +346,21 @@ func (s *Store) CreateEventResponse(ctx context.Context, cmd CreateEventResponse
 		return
 	}
 
-	const responseQuery = `INSERT INTO response(event_id, id, guest_name) VALUES (?, ?, ?);`
+	const responseQuery = `
+		INSERT INTO response(event_id, id, guest_name)
+		VALUES (?, ?, ?);`
 	err = sqlitex.Exec(conn, responseQuery, nil, cmd.EventID, responseID, cmd.GuestName)
 	if err != nil {
 		return
 	}
 
-	const responseTimeQuery = `INSERT INTO response_time(response_id, date, time) VALUES (?, ?, ?);`
+	const responseTimeQuery = `
+		INSERT INTO response_time(event_id, response_id, date, time)
+		VALUES (?, ?, ?, ?);`
 	for d, hs := range cmd.DateHours {
 		for h := range hs {
-			err = sqlitex.Exec(conn, responseTimeQuery, nil, responseID, d.Format(dbDateLayout), h)
+			err = sqlitex.Exec(conn, responseTimeQuery, nil,
+				cmd.EventID, responseID, d.Format(dbDateLayout), h)
 			if err != nil {
 				return
 			}
@@ -403,7 +410,7 @@ func (s *Store) GetEventResponse(ctx context.Context, query GetEventResponseQuer
 	const responseTimeQuery = `
 		SELECT date, time
 		FROM response_time
-		WHERE response_id = ?`
+		WHERE  event_id = ? AND response_id = ?`
 	err = sqlitex.Exec(conn, responseTimeQuery,
 		func(stmt *sqlite.Stmt) error {
 			d, err := date.Parse(dbDateLayout, stmt.ColumnText(0))
@@ -415,7 +422,7 @@ func (s *Store) GetEventResponse(ctx context.Context, query GetEventResponseQuer
 			}
 			result.DateHours[d][stmt.ColumnInt(1)] = struct{}{}
 			return nil
-		}, query.ResponseID)
+		}, query.EventID, query.ResponseID)
 	if err != nil {
 		return GetEventResponseResult{}, err
 	}
diff --git a/todo.txt b/todo.txt
index e1e54c2..2dca8a4 100644
--- a/todo.txt
+++ b/todo.txt
@@ -1,6 +1,8 @@
 Essential:
 ------------
 Show response after submission
+Add a schema ID to the DB
+Move front and back into internal
 Require earliest and latest dates for creation
 Ensure latest date is at least earliest date
 Ensure date span is within a maximum
@@ -9,7 +11,6 @@ Prevent blank event names and guest names
 
 Cleanup:
 ------------
-Give response (and therefore response_time) a composite key
 Get rid of the Stat call in NewStore.
     I can't remember the details. I think the old version
     of sqlitex was panicking if I failed to open a DB file.