diff --git a/packages/backend/src/core/FeaturedService.ts b/packages/backend/src/core/FeaturedService.ts
index 78309e42e5..5963b7fc39 100644
--- a/packages/backend/src/core/FeaturedService.ts
+++ b/packages/backend/src/core/FeaturedService.ts
@@ -15,7 +15,7 @@ const GLOBAL_NOTES_RANKING_WINDOW = 1000 * 60 * 60 * 24 * 3; // 3日ごと
 export class FeaturedService {
 	constructor(
 		@Inject(DI.redis)
-		private redisClient: Redis.Redis,
+		private redisClient: Redis.Redis, // TODO: 専用のRedisサーバーを設定できるようにする
 	) {
 	}
 
@@ -26,103 +26,75 @@ export class FeaturedService {
 	}
 
 	@bindThis
-	private getCurrentGlobalNotesRankingWindow(): number {
+	private getCurrentWindow(windowRange: number): number {
 		const passed = new Date().getTime() - new Date(new Date().getFullYear(), 0, 1).getTime();
-		return Math.floor(passed / GLOBAL_NOTES_RANKING_WINDOW);
+		return Math.floor(passed / windowRange);
+	}
+
+	@bindThis
+	private async updateRankingOf(name: string, windowRange: number, element: string, score = 1): Promise<void> {
+		const currentWindow = this.getCurrentWindow(windowRange);
+		const redisTransaction = this.redisClient.multi();
+		redisTransaction.zincrby(
+			`${name}:${currentWindow}`,
+			score,
+			element);
+		redisTransaction.expire(
+			`${name}:${currentWindow}`,
+			(windowRange * 3) / 1000,
+			'NX'); // "NX -- Set expiry only when the key has no expiry" = 有効期限がないときだけ設定
+		await redisTransaction.exec();
+	}
+
+	@bindThis
+	private async getRankingOf(name: string, windowRange: number, limit: number): Promise<string[]> {
+		const currentWindow = this.getCurrentWindow(windowRange);
+		const previousWindow = currentWindow - 1;
+
+		const [currentRankingResult, previousRankingResult] = await Promise.all([
+			this.redisClient.zrange(
+				`${name}:${currentWindow}`, 0, limit, 'REV', 'WITHSCORES'),
+			this.redisClient.zrange(
+				`${name}:${previousWindow}`, 0, limit, 'REV', 'WITHSCORES'),
+		]);
+
+		const ranking = new Map<string, number>();
+		for (let i = 0; i < currentRankingResult.length; i += 2) {
+			const noteId = currentRankingResult[i];
+			const score = parseInt(currentRankingResult[i + 1], 10);
+			ranking.set(noteId, score);
+		}
+		for (let i = 0; i < previousRankingResult.length; i += 2) {
+			const noteId = previousRankingResult[i];
+			const score = parseInt(previousRankingResult[i + 1], 10);
+			const exist = ranking.get(noteId);
+			if (exist != null) {
+				ranking.set(noteId, (exist + score) / 2);
+			} else {
+				ranking.set(noteId, score);
+			}
+		}
+
+		return Array.from(ranking.keys());
 	}
 
 	@bindThis
 	public async updateGlobalNotesRanking(noteId: MiNote['id'], score = 1): Promise<void> {
-		// TODO: フォロワー数の多い人が常にランキング上位になるのを防ぎたい
-		const currentWindow = this.getCurrentGlobalNotesRankingWindow();
-		const redisTransaction = this.redisClient.multi();
-		redisTransaction.zincrby(
-			`featuredGlobalNotesRanking:${currentWindow}`,
-			score.toString(),
-			noteId);
-		redisTransaction.expire(
-			`featuredGlobalNotesRanking:${currentWindow}`,
-			(GLOBAL_NOTES_RANKING_WINDOW * 3) / 1000,
-			'NX'); // "NX -- Set expiry only when the key has no expiry" = 有効期限がないときだけ設定
-		await redisTransaction.exec();
+		return this.updateRankingOf('featuredGlobalNotesRanking', GLOBAL_NOTES_RANKING_WINDOW, noteId, score);
 	}
 
 	@bindThis
 	public async updateInChannelNotesRanking(noteId: MiNote['id'], channelId: MiNote['channelId'], score = 1): Promise<void> {
-		const currentWindow = this.getCurrentGlobalNotesRankingWindow();
-		const redisTransaction = this.redisClient.multi();
-		redisTransaction.zincrby(
-			`featuredInChannelNotesRanking:${channelId}:${currentWindow}`,
-			score.toString(),
-			noteId);
-		redisTransaction.expire(
-			`featuredInChannelNotesRanking:${channelId}:${currentWindow}`,
-			(GLOBAL_NOTES_RANKING_WINDOW * 3) / 1000,
-			'NX'); // "NX -- Set expiry only when the key has no expiry" = 有効期限がないときだけ設定
-		await redisTransaction.exec();
+		return this.updateRankingOf(`featuredInChannelNotesRanking:${channelId}`, GLOBAL_NOTES_RANKING_WINDOW, noteId, score);
 	}
 
 	@bindThis
 	public async getGlobalNotesRanking(limit: number): Promise<MiNote['id'][]> {
-		const currentWindow = this.getCurrentGlobalNotesRankingWindow();
-		const previousWindow = currentWindow - 1;
-
-		const [currentRankingResult, previousRankingResult] = await Promise.all([
-			this.redisClient.zrange(
-				`featuredGlobalNotesRanking:${currentWindow}`, 0, limit, 'REV', 'WITHSCORES'),
-			this.redisClient.zrange(
-				`featuredGlobalNotesRanking:${previousWindow}`, 0, limit, 'REV', 'WITHSCORES'),
-		]);
-
-		const ranking = new Map<MiNote['id'], number>();
-		for (let i = 0; i < currentRankingResult.length; i += 2) {
-			const noteId = currentRankingResult[i];
-			const score = parseInt(currentRankingResult[i + 1], 10);
-			ranking.set(noteId, score);
-		}
-		for (let i = 0; i < previousRankingResult.length; i += 2) {
-			const noteId = previousRankingResult[i];
-			const score = parseInt(previousRankingResult[i + 1], 10);
-			const exist = ranking.get(noteId);
-			if (exist != null) {
-				ranking.set(noteId, (exist + score) / 2);
-			} else {
-				ranking.set(noteId, score);
-			}
-		}
-
-		return Array.from(ranking.keys());
+		return this.getRankingOf('featuredGlobalNotesRanking', GLOBAL_NOTES_RANKING_WINDOW, limit);
 	}
 
 	@bindThis
 	public async getInChannelNotesRanking(channelId: MiNote['channelId'], limit: number): Promise<MiNote['id'][]> {
-		const currentWindow = this.getCurrentGlobalNotesRankingWindow();
-		const previousWindow = currentWindow - 1;
-
-		const [currentRankingResult, previousRankingResult] = await Promise.all([
-			this.redisClient.zrange(
-				`featuredInChannelNotesRanking:${channelId}:${currentWindow}`, 0, limit, 'REV', 'WITHSCORES'),
-			this.redisClient.zrange(
-				`featuredInChannelNotesRanking:${channelId}:${previousWindow}`, 0, limit, 'REV', 'WITHSCORES'),
-		]);
-
-		const ranking = new Map<MiNote['id'], number>();
-		for (let i = 0; i < currentRankingResult.length; i += 2) {
-			const noteId = currentRankingResult[i];
-			const score = parseInt(currentRankingResult[i + 1], 10);
-			ranking.set(noteId, score);
-		}
-		for (let i = 0; i < previousRankingResult.length; i += 2) {
-			const noteId = previousRankingResult[i];
-			const score = parseInt(previousRankingResult[i + 1], 10);
-			const exist = ranking.get(noteId);
-			if (exist != null) {
-				ranking.set(noteId, (exist + score) / 2);
-			} else {
-				ranking.set(noteId, score);
-			}
-		}
-
-		return Array.from(ranking.keys());
+		return this.getRankingOf(`featuredInChannelNotesRanking:${channelId}`, GLOBAL_NOTES_RANKING_WINDOW, limit);
 	}
 }