diff --git a/database/create-indexes.js b/database/create-indexes.js
new file mode 100644
index 000000000..267b4db66
--- /dev/null
+++ b/database/create-indexes.js
@@ -0,0 +1,77 @@
+/**
+ * Idempotent index-creation script.
+ *
+ * Creates the MongoDB indexes that the application's existing queries already
+ * filter and sort on. Adding a btree index never changes query results: it only
+ * speeds up filters/sorts on the indexed fields, so this script is purely
+ * additive and changes no query or search semantics (in particular, the
+ * unanchored `$regex` substring search is unaffected).
+ *
+ * `createIndex` is idempotent: it is a no-op if an equivalent index already
+ * exists, and modern MongoDB builds indexes non-blocking, so this script is
+ * safe to re-run. It must be run by an operator against the database, e.g.
+ * `npm run create-indexes`.
+ */
+
+import { sets, packets, tossups, bonuses } from './qbreader/collections.js';
+import { tossupStars, bonusStars, perTossupData, perBonusData } from './account-info/collections.js';
+
+// Each entry: [Mongo collection handle, index key spec, human-readable note]
+const INDEXES = [
+  // --- qbreader: tossups / bonuses ---------------------------------------
+  // get-query sort `{ 'set.name': -1, 'packet.number': 1, number: 1 }`;
+  // also serves get-set / get-pg-lookup filters and sorts on set.name + packet.number.
+  [tossups, { 'set.name': -1, 'packet.number': 1, number: 1 }, 'tossups by set.name/packet.number/number (query & set listing sort)'],
+  [bonuses, { 'set.name': -1, 'packet.number': 1, number: 1 }, 'bonuses by set.name/packet.number/number (query & set listing sort)'],
+
+  // get-random-tossups / get-random-bonuses range match on set.year; also
+  // used by get-frequency-list and get-query year filters.
+  [tossups, { 'set.year': 1 }, 'tossups by set.year (random / frequency / year-range filters)'],
+  [bonuses, { 'set.year': 1 }, 'bonuses by set.year (random / frequency / year-range filters)'],
+
+  // get-packet finds tossups/bonuses by packet._id sorted by number; also the
+  // join field for packet-metadata-list $lookup.
+  [tossups, { 'packet._id': 1, number: 1 }, 'tossups by packet._id/number (get-packet & packet-metadata lookup)'],
+  [bonuses, { 'packet._id': 1, number: 1 }, 'bonuses by packet._id/number (get-packet & packet-metadata lookup)'],
+
+  // --- qbreader: packets -------------------------------------------------
+  // get-packet findOne({ 'set.name', number }); get-num-packets countDocuments({ 'set.name' });
+  // get-packet-list find({ 'set.name' }).
+  [packets, { 'set.name': 1, number: 1 }, 'packets by set.name/number (get-packet, get-num-packets, get-packet-list)'],
+  // packet-metadata-list $match on set._id.
+  [packets, { 'set._id': 1 }, 'packets by set._id (packet-metadata-list)'],
+
+  // --- qbreader: sets ----------------------------------------------------
+  // get-set-id / rename-set findOne({ name }).
+  [sets, { name: 1 }, 'sets by name (get-set-id, rename-set lookups)'],
+
+  // --- account-info: tossup-stars / bonus-stars --------------------------
+  // get-ids-*, is-starred-*, star-*, unstar-*, clear-* all filter on user_id.
+  [tossupStars, { user_id: 1 }, 'tossup-stars by user_id (star lookups/updates)'],
+  [bonusStars, { user_id: 1 }, 'bonus-stars by user_id (star lookups/updates)'],
+
+  // --- account-info: per-tossup-data / per-bonus-data --------------------
+  // leaderboard groups on data.user_id; user-stats match documents lead with
+  // data.user_id (perf report's recommended index).
+  [perTossupData, { 'data.user_id': 1 }, 'per-tossup-data by data.user_id (leaderboard & user-stats)'],
+  [perBonusData, { 'data.user_id': 1 }, 'per-bonus-data by data.user_id (leaderboard & user-stats)'],
+  // user-stats match documents also filter on set_id.
+  [perTossupData, { set_id: 1 }, 'per-tossup-data by set_id (user-stats set filter)'],
+  [perBonusData, { set_id: 1 }, 'per-bonus-data by set_id (user-stats set filter)']
+];
+
+async function main () {
+  for (const [collection, keys, note] of INDEXES) {
+    const name = await collection.createIndex(keys);
+    console.log(`ensured index ${name} on ${collection.namespace} — ${note}`);
+  }
+  console.log(`done: ensured ${INDEXES.length} indexes`);
+}
+
+try {
+  await main();
+  process.exit(0);
+} catch (error) {
+  console.error('failed to create indexes:', error);
+  process.exit(1);
+}
diff --git a/package.json b/package.json
index 9b664feaa..ec903cbda 100644
--- a/package.json
+++ b/package.json
@@ -4,6 +4,7 @@
     "type": "module",
     "scripts": {
         "build": "npm run webpack && npm run sass",
+        "create-indexes": "node database/create-indexes.js",
         "dev": "npm run build && npm run start",
         "lint": "npx semistandard --fix",
         "sass": "sass scss/custom.scss client/style.css --style compressed",