a few changes to make A/B testing easier

server/routes/exists.js

@@ -0,0 +1,19 @@
+const storage = require('../storage');
+
+function validateID(route_id) {
+  return route_id.match(/^[0-9a-fA-F]{10}$/) !== null;
+}
+
+module.exports = async (req, res) => {
+  const id = req.params.id;
+  if (!validateID(id)) {
+    return res.sendStatus(404);
+  }
+
+  try {
+    await storage.exists(id);
+    res.sendStatus(200);
+  } catch (e) {
+    res.sendStatus(404);
+  }
+};