diff --git a/.config/example.yml b/.config/example.yml
index 24985fd28..32ad16562 100644
--- a/.config/example.yml
+++ b/.config/example.yml
@@ -127,19 +127,11 @@ drive:
 # change it according to your preferences.
 
 # Available methods:
-# aid1 ... Use AID for ID generation (with random 1 char)
-# aid2 ... Use AID for ID generation (with random 2 chars)
-# aid3 ... Use AID for ID generation (with random 3 chars)
-# aid4 ... Use AID for ID generation (with random 4 chars)
+# aid ... Use AID for ID generation
 # ulid ... Use ulid for ID generation
 # objectid ... This is left for backward compatibility.
 
-# AID(n) is the original ID generation method.
-# The trailing n represents the number of random characters that
-# will be suffixed.
-# The larger n is the safer. If n is small, the possibility of
-# collision at the same time increases, but there are also
-# advantages such as shortening of the URL.
+# AID is the original ID generation method.
 
 # ULID: Universally Unique Lexicographically Sortable Identifier.
 # for more details: https://github.com/ulid/spec
@@ -148,7 +140,7 @@ drive:
 # ObjectID is the method used in previous versions of Misskey.
 # * Choose this if you are migrating from a previous Misskey.
 
-id: 'aid2'
+id: 'aid'
 
 #   ┌─────────────────────┐
 #───┘ Other configuration └─────────────────────────────────────
diff --git a/src/misc/aid.ts b/src/misc/aid.ts
deleted file mode 100644
index aba53ed5f..000000000
--- a/src/misc/aid.ts
+++ /dev/null
@@ -1,26 +0,0 @@
-// AID
-// 長さ8の[2000年1月1日からの経過ミリ秒をbase36でエンコードしたもの] + 長さnの[ランダムな文字列]
-
-const CHARS = '0123456789abcdefghijklmnopqrstuvwxyz';
-const TIME2000 = 946684800000;
-
-function getTime(time: number) {
-	time = time - TIME2000;
-	if (time < 0) time = 0;
-
-	return time.toString(36);
-}
-
-function getRandom(length: number) {
-	let str = '';
-
-	for (let i = 0; i < length; i++) {
-		str += CHARS[Math.floor(Math.random() * CHARS.length)];
-	}
-
-	return str;
-}
-
-export function genAid(date: Date, rand: number): string {
-	return getTime(date.getTime()).padStart(8, CHARS[0]) + getRandom(rand);
-}
diff --git a/src/misc/aidc.ts b/src/misc/aidc.ts
deleted file mode 100644
index 75168ac30..000000000
--- a/src/misc/aidc.ts
+++ /dev/null
@@ -1,26 +0,0 @@
-// AID(Cheep)
-// 長さ6の[2000年1月1日からの経過秒をbase36でエンコードしたもの] + 長さ3の[ランダムな文字列]
-
-const CHARS = '0123456789abcdefghijklmnopqrstuvwxyz';
-const TIME2000 = 946684800000;
-
-function getTime(time: number) {
-	time = time - TIME2000;
-	if (time < 0) time = 0;
-	time = Math.floor(time / 1000);
-	return time.toString(36);
-}
-
-function getRandom() {
-	let str = '';
-
-	for (let i = 0; i < 3; i++) {
-		str += CHARS[Math.floor(Math.random() * CHARS.length)];
-	}
-
-	return str;
-}
-
-export function genAidc(date: Date): string {
-	return getTime(date.getTime()).padStart(6, CHARS[0]) + getRandom();
-}
diff --git a/src/misc/gen-id.ts b/src/misc/gen-id.ts
index fe901b1fe..d16910d01 100644
--- a/src/misc/gen-id.ts
+++ b/src/misc/gen-id.ts
@@ -1,7 +1,6 @@
 import { ulid } from 'ulid';
-import { genAid } from './aid';
-import { genAidc } from './aidc';
-import { genObjectId } from './object-id';
+import { genAid } from './id/aid';
+import { genObjectId } from './id/object-id';
 import config from '../config';
 
 const metohd = config.id.toLowerCase();
@@ -10,11 +9,7 @@ export function genId(date?: Date): string {
 	if (!date || (date > new Date())) date = new Date();
 
 	switch (metohd) {
-		case 'aidc': return genAidc(date);
-		case 'aid1': return genAid(date, 1);
-		case 'aid2': return genAid(date, 2);
-		case 'aid3': return genAid(date, 3);
-		case 'aid4': return genAid(date, 4);
+		case 'aid': return genAid(date);
 		case 'ulid': return ulid(date.getTime());
 		case 'objectid': return genObjectId(date);
 		default: throw 'unknown id generation method';
diff --git a/src/misc/id/aid.ts b/src/misc/id/aid.ts
new file mode 100644
index 000000000..7ab0a148e
--- /dev/null
+++ b/src/misc/id/aid.ts
@@ -0,0 +1,23 @@
+// AID
+// 長さ8の[2000年1月1日からの経過ミリ秒をbase36でエンコードしたもの] + 長さ2の[ノイズ文字列]
+
+import * as cluster from 'cluster';
+
+const TIME2000 = 946684800000;
+let counter = process.pid + (cluster.isMaster ? 0 : cluster.worker.id);
+
+function getTime(time: number) {
+	time = time - TIME2000;
+	if (time < 0) time = 0;
+
+	return time.toString(36).padStart(8, '0');
+}
+
+function getRandom() {
+	return counter.toString(36).padStart(length, '0').substr(2);
+}
+
+export function genAid(date: Date): string {
+	counter++;
+	return getTime(date.getTime()) + getRandom();
+}
diff --git a/src/misc/object-id.ts b/src/misc/id/object-id.ts
similarity index 89%
rename from src/misc/object-id.ts
rename to src/misc/id/object-id.ts
index 6f6422e5e..392ea4330 100644
--- a/src/misc/object-id.ts
+++ b/src/misc/id/object-id.ts
@@ -8,7 +8,7 @@ function getTime(time: number) {
 
 	time = Math.floor(time / 1000);
 
-	return time.toString(16);
+	return time.toString(16).padStart(8, CHARS[0]);
 }
 
 function getRandom() {