diff --git a/src/objects/news-do.ts b/src/objects/news-do.ts
index ed8010c6..21456bb8 100644
--- a/src/objects/news-do.ts
+++ b/src/objects/news-do.ts
@@ -5,7 +5,7 @@ import type { Env, Beat, Signal, SignalStatus, Streak, Brief, Classified, Classi
 import { validateSlug, validateHexColor, sanitizeString, validateDateFormat } from "../lib/validators";
 import { generateId, getPacificDate, getPacificYesterday, getPacificDayStartUTC, getPacificDayEndUTC, getNextDate } from "../lib/helpers";
 import { CLASSIFIED_DURATION_DAYS, CLASSIFIED_BRIEF_SLOTS, CLASSIFIED_BRIEF_MAX_CHARS, CLASSIFIED_STATUSES, SIGNAL_COOLDOWN_HOURS, BEAT_EXPIRY_DAYS, MAX_SIGNALS_PER_DAY, MAX_INCLUDED_SIGNALS_PER_BRIEF, MAX_APPROVED_SIGNALS_PER_DAY, SIGNAL_STATUSES, REVIEWABLE_SIGNAL_STATUSES, CONFIG_PUBLISHER_ADDRESS, BRIEF_INCLUSION_PAYOUT_SATS, WEEKLY_PRIZE_1ST_SATS, WEEKLY_PRIZE_2ND_SATS, WEEKLY_PRIZE_3RD_SATS, SCORING_WEIGHTS, PAYMENT_STAGE_TTL_MS } from "../lib/constants";
-import { SCHEMA_SQL, MIGRATION_PHASE0_SQL, MIGRATION_PAYMENTS_SQL, MIGRATION_BEAT_RESTRUCTURE_SQL, MIGRATION_SBTC_TRACKING_SQL, MIGRATION_CLASSIFIEDS_CLEANUP_SQL, MIGRATION_CLASSIFIEDS_REVIEW_SQL, MIGRATION_SNAPSHOTS_SQL, MIGRATION_BEAT_CLAIMS_SQL, MIGRATION_RETRACTION_SQL, MIGRATION_BEAT_NETWORK_FOCUS_SQL, MIGRATION_BITCOIN_MACRO_SQL, MIGRATION_QUANTUM_BEAT_SQL, MIGRATION_PAYMENT_STAGING_SQL, MIGRATION_APPROVAL_CAP_INDEX_SQL, MIGRATION_BEAT_EDITORS_SQL, MIGRATION_EDITORIAL_REVIEWS_SQL, MIGRATION_EDITOR_REVIEW_RATE_SQL, MIGRATION_CURATION_CLEANUP_SQL } from "./schema";
+import { SCHEMA_SQL, MIGRATION_PHASE0_SQL, MIGRATION_PAYMENTS_SQL, MIGRATION_BEAT_RESTRUCTURE_SQL, MIGRATION_SBTC_TRACKING_SQL, MIGRATION_CLASSIFIEDS_CLEANUP_SQL, MIGRATION_CLASSIFIEDS_REVIEW_SQL, MIGRATION_SNAPSHOTS_SQL, MIGRATION_BEAT_CLAIMS_SQL, MIGRATION_RETRACTION_SQL, MIGRATION_BEAT_NETWORK_FOCUS_SQL, MIGRATION_BITCOIN_MACRO_SQL, MIGRATION_QUANTUM_BEAT_SQL, MIGRATION_PAYMENT_STAGING_SQL, MIGRATION_APPROVAL_CAP_INDEX_SQL, MIGRATION_BEAT_EDITORS_SQL, MIGRATION_EDITORIAL_REVIEWS_SQL, MIGRATION_EDITOR_REVIEW_RATE_SQL, MIGRATION_CURATION_CLEANUP_SQL, MIGRATION_LEADERBOARD_INDEXES_SQL } from "./schema";
 
 // ── State machine transition maps ──
 // Hoisted to module level so they are created once and are testable.
@@ -285,7 +285,8 @@ export class NewsDO extends DurableObject<Env> {
     // 18 = Editorial reviews — type/score/factcheck columns on corrections table
     // 19 = Editor review rate — editor_review_rate_sats column on beats table
     // 20 = Curation cleanup — fix Mar 28-29 inscription IDs + void 312 orphaned earnings (#339)
-    const CURRENT_MIGRATION_VERSION = 20;
+    // 21 = Leaderboard composite indexes — accelerate 30-day rolling window queries (#319)
+    const CURRENT_MIGRATION_VERSION = 21;
     const versionRows = this.ctx.storage.sql
       .exec("SELECT value FROM config WHERE key = 'migration_version'")
       .toArray();
@@ -556,6 +557,21 @@ export class NewsDO extends DurableObject<Env> {
         }
       }
 
+      // Leaderboard composite indexes — accelerates 30-day rolling window
+      // subqueries in queryLeaderboard() from 5–10 s to <500 ms (issue #319).
+      if (appliedVersion < 21) {
+        for (const stmt of MIGRATION_LEADERBOARD_INDEXES_SQL) {
+          try {
+            this.ctx.storage.sql.exec(stmt);
+          } catch (e) {
+            const msg = e instanceof Error ? e.message : String(e);
+            if (!msg.includes("already exists")) {
+              console.error("Leaderboard indexes migration statement failed:", e);
+            }
+          }
+        }
+      }
+
       // Record current migration version so future cold starts skip all of the above.
       this.ctx.storage.sql.exec(
         "INSERT INTO config (key, value) VALUES ('migration_version', ?) ON CONFLICT(key) DO UPDATE SET value = excluded.value, updated_at = datetime('now')",
diff --git a/src/objects/schema.ts b/src/objects/schema.ts
index 5b94017e..fdc34d2a 100644
--- a/src/objects/schema.ts
+++ b/src/objects/schema.ts
@@ -601,3 +601,24 @@ export const MIGRATION_CURATION_CLEANUP_SQL = [
        'db837a01-788d-4f08-a174-8758347ce61a','ffcb4de3-3998-4265-a8a2-eb8944f4af32','43800ead-c4bd-46ef-95f2-5cd1a1ae50a9','80e3529a-a4e9-4cd5-b41c-bcb701a0ba53','2b4cfe7a-75d0-4ce0-906a-bff3e09185cc','2e00e3ef-a979-4583-b010-7565d9b8e635','31cf9975-c3af-44d5-ba5c-b7e5f11375af','dc06393c-f1e0-4667-8ee0-3a593f39ff2c','248db72c-6082-43ca-8500-3c39b013c5e2','f74eb37a-cfba-47d4-adc9-06b62422e2b8','cef57500-2ee9-4c12-82eb-5cb3f8f03e52','3960c10e-92f8-43f6-b8bb-58f768dc5fc0','40d30fbb-459b-49ea-8f94-98b2c8d17a0c','52fadd57-8847-46a8-85e7-d8458f86374e','747ef5c5-30fc-4bff-a555-d52b982dcd4d','cb05bbc3-ed0c-4f77-8ec3-5c7e916bd796','772617b2-2c1b-4f61-bb50-2203b623787a','a1518f55-d566-47d0-a397-35ef9a50efd4','7d995511-db66-400c-8d26-ad198c985281','9f6d8223-aeb5-4de0-b2ab-1ecff104dcdc','545f7829-a536-464c-9417-6c06fa26d02a','bcd9e7ef-992c-4a80-b788-c7000fba15c7','14305d91-2348-4299-b26d-3a4bfebd2909','41bf9018-b15e-4995-9699-fcdb9357634f','b5e4f967-76f5-4012-9c64-c6369f010482','4f5f50e0-60f6-4901-aae7-a0468c61234b','8b866fc7-e02d-4a6f-ba88-fed94434466b','10c5c979-a1e9-45d8-92a4-59fe7d70bd2a','246983df-bd20-4d24-8dce-88b526284e82','45c3be21-17b1-41ca-ab18-82a2ec165146'
      )`,
 ] as const;
+
+/**
+ * Migration 21 — Leaderboard composite indexes.
+ * Adds composite indexes to accelerate the 30-day rolling window subqueries
+ * in queryLeaderboard(). Without these, each LEFT JOIN subquery performs a
+ * full table scan on every leaderboard request (10s+ for tables with 1k+ rows).
+ *
+ * Indexes added:
+ *   - signals(correction_of, created_at)      — covers the correction_of IS NULL + 30-day filter
+ *   - brief_signals(created_at, retracted_at)  — covers the 30-day window + retracted_at IS NULL filter
+ *   - corrections(status, created_at)          — covers the status='approved' + 30-day filter
+ *   - referral_credits(credited_at)            — covers the credited_at IS NOT NULL + 30-day filter
+ *
+ * Expected improvement: 5–10 s → <500 ms per arc0btc's analysis (issue #319).
+ */
+export const MIGRATION_LEADERBOARD_INDEXES_SQL = [
+  "CREATE INDEX IF NOT EXISTS idx_signals_correction_created ON signals(correction_of, created_at)",
+  "CREATE INDEX IF NOT EXISTS idx_brief_signals_created_retracted ON brief_signals(created_at, retracted_at)",
+  "CREATE INDEX IF NOT EXISTS idx_corrections_status_created ON corrections(status, created_at)",
+  "CREATE INDEX IF NOT EXISTS idx_referral_credits_credited ON referral_credits(credited_at)",
+] as const;