diff --git a/app/features/leaderboards/LeaderboardRepository.server.ts b/app/features/leaderboards/LeaderboardRepository.server.ts
index a3147eb56..6d8dc5446 100644
--- a/app/features/leaderboards/LeaderboardRepository.server.ts
+++ b/app/features/leaderboards/LeaderboardRepository.server.ts
@@ -14,7 +14,6 @@ import {
 	concatUserSubmittedImagePrefix,
 } from "~/utils/kysely.server";
 import { dateToDatabaseTimestamp } from "../../utils/dates";
-import invariant from "../../utils/invariant";
 import * as Seasons from "../mmr/core/Seasons";
 import { ordinalToSp } from "../mmr/mmr-utils";
 import {
@@ -140,44 +139,24 @@ async function filterOutNonSqPlayers(args: {
 }
 
 async function userIdsWithEnoughSqMatchesForTeamLeaderboard(seasonNth: number) {
-	const season = Seasons.nthToDateRange(seasonNth);
-	invariant(season, "Season not found in sqMatchCountByUserId");
-
-	const userIds = await db
-		.selectFrom("GroupMatch")
-		.innerJoin("GroupMember", (join) =>
-			join.on((eb) =>
-				eb.or([
-					eb("GroupMatch.alphaGroupId", "=", eb.ref("GroupMember.groupId")),
-					eb("GroupMatch.bravoGroupId", "=", eb.ref("GroupMember.groupId")),
-				]),
-			),
-		)
-		// this join is needed to filter out canceled matches
-		.innerJoin("Skill", (join) =>
-			join
-				.onRef("Skill.groupMatchId", "=", "GroupMatch.id")
-				.onRef("Skill.userId", "=", "GroupMember.userId"),
-		)
-		.select("GroupMember.userId")
-		.where("GroupMatch.createdAt", ">", dateToDatabaseTimestamp(season.starts))
-		.where(
-			"GroupMatch.createdAt",
-			"<",
-			dateToDatabaseTimestamp(add(season.ends, { days: 1 })), // some matches can be finished after the season ends
+	// a Skill row with groupMatchId set exists exactly once per user per
+	// completed (not canceled) SendouQ match of the season
+	const rows = await db
+		.selectFrom("Skill")
+		.select("userId")
+		.where("season", "=", seasonNth)
+		.where("groupMatchId", "is not", null)
+		.where("userId", "is not", null)
+		.groupBy("userId")
+		.having(
+			(eb) => eb.fn.countAll(),
+			">=",
+			MATCHES_COUNT_NEEDED_FOR_LEADERBOARD,
 		)
+		.$narrowType<{ userId: number }>()
 		.execute();
 
-	const countsMap = new Map<number, number>();
-
-	for (const { userId } of userIds) {
-		const count = countsMap.get(userId) ?? 0;
-		countsMap.set(userId, count + 1);
-	}
-
-	return Array.from(countsMap.entries())
-		.filter(([_userId, count]) => count >= MATCHES_COUNT_NEEDED_FOR_LEADERBOARD)
-		.map(([userId]) => userId);
+	return rows.map((row) => row.userId);
 }
 
 export async function userHasEnoughSqMatches(userId: number) {
@@ -308,34 +287,50 @@ function xpLeaderboardQuery(where?: {
 	mode?: RankedModeShort;
 	weaponSplId?: MainWeaponId;
 }) {
-	let query = db
-		.selectFrom("XRankPlacement")
-		.innerJoin("SplatoonPlayer", "SplatoonPlayer.id", "XRankPlacement.playerId")
+	// aggregating before joining keeps the group-by an index-only scan and the
+	// player/user joins limited to one lookup per player instead of per placement
+	return db
+		.selectFrom((eb) => {
+			let placements = eb
+				.selectFrom("XRankPlacement")
+				.select(({ fn }) => [
+					"XRankPlacement.id as entryId",
+					"XRankPlacement.playerId",
+					"XRankPlacement.weaponSplId",
+					"XRankPlacement.name",
+					fn.max("XRankPlacement.power").as("power"),
+				])
+				.groupBy("XRankPlacement.playerId");
+
+			if (where?.mode) {
+				placements = placements.where("XRankPlacement.mode", "=", where.mode);
+			}
+
+			if (typeof where?.weaponSplId === "number") {
+				placements = placements.where(
+					"XRankPlacement.weaponSplId",
+					"=",
+					where.weaponSplId,
+				);
+			}
+
+			return placements.as("Placement");
+		})
+		.innerJoin("SplatoonPlayer", "SplatoonPlayer.id", "Placement.playerId")
 		.leftJoin("User", "User.id", "SplatoonPlayer.userId")
-		.select(({ fn }) => [
+		.select([
 			...COMMON_USER_FIELDS,
-			"XRankPlacement.id as entryId",
-			"XRankPlacement.playerId",
-			"XRankPlacement.weaponSplId",
-			"XRankPlacement.name",
-			fn.max("XRankPlacement.power").as("power"),
-			sql<number>`rank() over (order by max("XRankPlacement"."power") desc)`.as(
+			"Placement.entryId",
+			"Placement.playerId",
+			"Placement.weaponSplId",
+			"Placement.name",
+			"Placement.power",
+			sql<number>`rank() over (order by "Placement"."power" desc)`.as(
 				"placementRank",
 			),
 		])
-		.groupBy("XRankPlacement.playerId")
-		.orderBy("power", "desc")
+		.orderBy("Placement.power", "desc")
 		.limit(DEFAULT_LEADERBOARD_MAX_SIZE);
-
-	if (where?.mode) {
-		query = query.where("XRankPlacement.mode", "=", where.mode);
-	}
-
-	if (typeof where?.weaponSplId === "number") {
-		query = query.where("XRankPlacement.weaponSplId", "=", where.weaponSplId);
-	}
-
-	return query;
 }
 
 export async function allXPLeaderboard() {
diff --git a/db-test.sqlite3 b/db-test.sqlite3
index 4a77801e0..c8f0ae359 100644
Binary files a/db-test.sqlite3 and b/db-test.sqlite3 differ
diff --git a/e2e/seeds/db-seed-AB_RR.sqlite3 b/e2e/seeds/db-seed-AB_RR.sqlite3
index 6dde92e40..8a1ab387a 100644
Binary files a/e2e/seeds/db-seed-AB_RR.sqlite3 and b/e2e/seeds/db-seed-AB_RR.sqlite3 differ
diff --git a/e2e/seeds/db-seed-DEFAULT.sqlite3 b/e2e/seeds/db-seed-DEFAULT.sqlite3
index 45148f279..76525f3fd 100644
Binary files a/e2e/seeds/db-seed-DEFAULT.sqlite3 and b/e2e/seeds/db-seed-DEFAULT.sqlite3 differ
diff --git a/e2e/seeds/db-seed-FINALIZED_BRACKET.sqlite3 b/e2e/seeds/db-seed-FINALIZED_BRACKET.sqlite3
index 57bc26574..395b11477 100644
Binary files a/e2e/seeds/db-seed-FINALIZED_BRACKET.sqlite3 and b/e2e/seeds/db-seed-FINALIZED_BRACKET.sqlite3 differ
diff --git a/e2e/seeds/db-seed-IN_SQ_MATCH.sqlite3 b/e2e/seeds/db-seed-IN_SQ_MATCH.sqlite3
index 31f30c509..c0243f7ec 100644
Binary files a/e2e/seeds/db-seed-IN_SQ_MATCH.sqlite3 and b/e2e/seeds/db-seed-IN_SQ_MATCH.sqlite3 differ
diff --git a/e2e/seeds/db-seed-NO_SCRIMS.sqlite3 b/e2e/seeds/db-seed-NO_SCRIMS.sqlite3
index 1ecfc155b..b56fd0087 100644
Binary files a/e2e/seeds/db-seed-NO_SCRIMS.sqlite3 and b/e2e/seeds/db-seed-NO_SCRIMS.sqlite3 differ
diff --git a/e2e/seeds/db-seed-NO_SQ_GROUPS.sqlite3 b/e2e/seeds/db-seed-NO_SQ_GROUPS.sqlite3
index 7f6e4b193..2065f894a 100644
Binary files a/e2e/seeds/db-seed-NO_SQ_GROUPS.sqlite3 and b/e2e/seeds/db-seed-NO_SQ_GROUPS.sqlite3 differ
diff --git a/e2e/seeds/db-seed-NO_TOURNAMENT_TEAMS.sqlite3 b/e2e/seeds/db-seed-NO_TOURNAMENT_TEAMS.sqlite3
index d39e87c0f..26a6ec19b 100644
Binary files a/e2e/seeds/db-seed-NO_TOURNAMENT_TEAMS.sqlite3 and b/e2e/seeds/db-seed-NO_TOURNAMENT_TEAMS.sqlite3 differ
diff --git a/e2e/seeds/db-seed-NZAP_IN_TEAM.sqlite3 b/e2e/seeds/db-seed-NZAP_IN_TEAM.sqlite3
index 9cbbe0691..5a8dbdf4a 100644
Binary files a/e2e/seeds/db-seed-NZAP_IN_TEAM.sqlite3 and b/e2e/seeds/db-seed-NZAP_IN_TEAM.sqlite3 differ
diff --git a/e2e/seeds/db-seed-REG_OPEN.sqlite3 b/e2e/seeds/db-seed-REG_OPEN.sqlite3
index 0d61ed97d..c8a5c22de 100644
Binary files a/e2e/seeds/db-seed-REG_OPEN.sqlite3 and b/e2e/seeds/db-seed-REG_OPEN.sqlite3 differ
diff --git a/e2e/seeds/db-seed-SMALL_SOS.sqlite3 b/e2e/seeds/db-seed-SMALL_SOS.sqlite3
index 23177b693..af6c825d3 100644
Binary files a/e2e/seeds/db-seed-SMALL_SOS.sqlite3 and b/e2e/seeds/db-seed-SMALL_SOS.sqlite3 differ
diff --git a/e2e/seeds/db-seed-TEAM_MAP_PREFS.sqlite3 b/e2e/seeds/db-seed-TEAM_MAP_PREFS.sqlite3
index b6e1910d5..b0cc4e6cd 100644
Binary files a/e2e/seeds/db-seed-TEAM_MAP_PREFS.sqlite3 and b/e2e/seeds/db-seed-TEAM_MAP_PREFS.sqlite3 differ
diff --git a/migrations/146-leaderboard-indexes.js b/migrations/146-leaderboard-indexes.js
new file mode 100644
index 000000000..ff1c55815
--- /dev/null
+++ b/migrations/146-leaderboard-indexes.js
@@ -0,0 +1,23 @@
+export function up(db) {
+	db.transaction(() => {
+		// Covering index for season-scoped per-user Skill aggregates: the user SP
+		// leaderboard's latest-skill-per-user group-by and the SQ match count
+		// (groupMatchId included so neither needs rowid lookups).
+		db.prepare(
+			/* sql */ `create index skill_season_user_id_group_match_id on "Skill"("season", "userId", "groupMatchId")`,
+		).run();
+
+		// Covering index for the team leaderboard's latest-skill-per-identifier
+		// group-by (previously filtered via skill_season + temp B-tree).
+		db.prepare(
+			/* sql */ `create index skill_season_identifier on "Skill"("season", "identifier")`,
+		).run();
+
+		// Covering index for the XP leaderboards' max(power) per player group-by;
+		// mode/weaponSplId/name included so the all/mode/weapon variants are all
+		// answered without touching the table.
+		db.prepare(
+			/* sql */ `create index xrank_placement_player_power on "XRankPlacement"("playerId", "power", "mode", "weaponSplId", "name")`,
+		).run();
+	})();
+}