diff --git a/src/localdb.ts b/src/localdb.ts
index 806eb8a..1473289 100644
--- a/src/localdb.ts
+++ b/src/localdb.ts
@@ -1,10 +1,13 @@
 import * as lf from "lovefield-ts/dist/es6/lf.js";
 import { TAbstractFile, TFile, TFolder } from "obsidian";
 
+import type { SUPPORTED_SERVICES_TYPE } from "./misc";
+
 export type DatabaseConnection = lf.DatabaseConnection;
 
 export const DEFAULT_DB_NAME = "saveremotedb";
 export const DEFAULT_TBL_DELETE_HISTORY = "filefolderoperationhistory";
+export const DEFAULT_TBL_SYNC_MAPPING = "syncmetadatahistory";
 
 export interface FileFolderHistoryRecord {
   key: string;
@@ -17,7 +20,19 @@ export interface FileFolderHistoryRecord {
   rename_to: string;
 }
 
-export const prepareDB = async () => {
+export interface SyncMetaMappingRecord {
+  local_key: string;
+  remote_key: string;
+  local_size: number;
+  remote_size: number;
+  local_mtime: number;
+  remote_mtime: number;
+  remote_extra_key: string;
+  remote_type: SUPPORTED_SERVICES_TYPE;
+  key_type: "folder" | "file";
+}
+
+export const prepareDBs = async () => {
   const schemaBuilder = lf.schema.create(DEFAULT_DB_NAME, 1);
   schemaBuilder
     .createTable(DEFAULT_TBL_DELETE_HISTORY)
@@ -31,6 +46,28 @@ export const prepareDB = async () => {
     .addColumn("key_type", lf.Type.STRING)
     .addPrimaryKey(["id"], true)
     .addIndex("idxKey", ["key"]);
+
+  schemaBuilder
+    .createTable(DEFAULT_TBL_SYNC_MAPPING)
+    .addColumn("id", lf.Type.INTEGER)
+    .addColumn("local_key", lf.Type.STRING)
+    .addColumn("remote_key", lf.Type.STRING)
+    .addColumn("local_size", lf.Type.INTEGER)
+    .addColumn("remote_size", lf.Type.INTEGER)
+    .addColumn("local_mtime", lf.Type.INTEGER)
+    .addColumn("remote_mtime", lf.Type.INTEGER)
+    .addColumn("key_type", lf.Type.STRING)
+    .addColumn("remote_extra_key", lf.Type.STRING)
+    .addColumn("remote_type", lf.Type.STRING)
+    .addNullable([
+      "remote_extra_key",
+      "remote_mtime",
+      "remote_size",
+      "local_mtime",
+    ])
+    .addPrimaryKey(["id"], true)
+    .addIndex("idxkey", ["local_key", "remote_key"]);
+
   const db = await schemaBuilder.connect({
     storeType: lf.DataStoreType.INDEXED_DB,
   });
@@ -38,7 +75,7 @@ export const prepareDB = async () => {
   return db;
 };
 
-export const destroyDB = async (db: lf.DatabaseConnection) => {
+export const destroyDBs = async (db: lf.DatabaseConnection) => {
   db.close();
   const req = indexedDB.deleteDatabase(DEFAULT_DB_NAME);
   req.onsuccess = (event) => {
@@ -53,7 +90,9 @@ export const destroyDB = async (db: lf.DatabaseConnection) => {
   };
 };
 
-export const loadHistoryTable = async (db: lf.DatabaseConnection) => {
+export const loadDeleteRenameHistoryTable = async (
+  db: lf.DatabaseConnection
+) => {
   const schema = db.getSchema().table(DEFAULT_TBL_DELETE_HISTORY);
   const tbl = db.getSchema().table(DEFAULT_TBL_DELETE_HISTORY);
 
@@ -66,7 +105,7 @@ export const loadHistoryTable = async (db: lf.DatabaseConnection) => {
   return records as FileFolderHistoryRecord[];
 };
 
-export const clearHistoryOfKey = async (
+export const clearDeleteRenameHistoryOfKey = async (
   db: lf.DatabaseConnection,
   key: string
 ) => {
@@ -155,9 +194,67 @@ export const insertRenameRecord = async (
   await db.insertOrReplace().into(tbl).values([row]).exec();
 };
 
-export const getAllRecords = async (db: lf.DatabaseConnection) => {
+export const getAllDeleteRenameRecords = async (db: lf.DatabaseConnection) => {
   const schema = db.getSchema().table(DEFAULT_TBL_DELETE_HISTORY);
   const res1 = await db.select().from(schema).exec();
   const res2 = res1 as FileFolderHistoryRecord[];
   return res2;
 };
+
+export const upsertSyncMetaMappingDataS3 = async (
+  db: lf.DatabaseConnection,
+  localKey: string,
+  localMTime: number,
+  localSize: number,
+  remoteKey: string,
+  remoteMTime: number,
+  remoteSize: number,
+  remoteExtraKey: string /* ETag from s3 */
+) => {
+  const schema = db.getSchema().table(DEFAULT_TBL_SYNC_MAPPING);
+  const aggregratedInfo: SyncMetaMappingRecord = {
+    local_key: localKey,
+    local_mtime: localMTime,
+    local_size: localSize,
+    remote_key: remoteKey,
+    remote_mtime: remoteMTime,
+    remote_size: remoteSize,
+    remote_extra_key: remoteExtraKey,
+    remote_type: "s3",
+    key_type: localKey.endsWith("/") ? "folder" : "file",
+  };
+  const row = schema.createRow(aggregratedInfo);
+  await db.insertOrReplace().into(schema).values([row]).exec();
+};
+
+export const getSyncMetaMappingByRemoteKeyS3 = async (
+  db: lf.DatabaseConnection,
+  remoteKey: string,
+  remoteMTime: number,
+  remoteExtraKey: string
+) => {
+  const schema = db.getSchema().table(DEFAULT_TBL_SYNC_MAPPING);
+  const tbl = db.getSchema().table(DEFAULT_TBL_SYNC_MAPPING);
+  const res = (await db
+    .select()
+    .from(tbl)
+    .where(
+      lf.op.and(
+        tbl.col("remote_key").eq(remoteKey),
+        tbl.col("remote_mtime").eq(remoteMTime),
+        tbl.col("remote_extra_key").eq(remoteExtraKey),
+        tbl.col("remote_type").eq("s3")
+      )
+    )
+    .exec()) as SyncMetaMappingRecord[];
+
+  if (res.length === 1) {
+    return res[0];
+  }
+
+  if (res.length === 0) {
+    return undefined;
+  }
+
+  throw Error("something bad in sync meta mapping!");
+};
diff --git a/src/main.ts b/src/main.ts
index 2014425..6d4356b 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -13,12 +13,12 @@ import {
 import * as CodeMirror from "codemirror";
 import type { DatabaseConnection } from "./localdb";
 import {
-  prepareDB,
-  destroyDB,
-  loadHistoryTable,
+  prepareDBs,
+  destroyDBs,
+  loadDeleteRenameHistoryTable,
   insertDeleteRecord,
   insertRenameRecord,
-  getAllRecords,
+  getAllDeleteRenameRecords,
 } from "./localdb";
 
 import type { SyncStatusType } from "./sync";
@@ -78,15 +78,16 @@ export default class SaveRemotePlugin extends Plugin {
       const s3Client = getS3Client(this.settings.s3);
       const remoteRsp = await listFromRemote(s3Client, this.settings.s3);
       const local = this.app.vault.getAllLoadedFiles();
-      const localHistory = await loadHistoryTable(this.db);
+      const localHistory = await loadDeleteRenameHistoryTable(this.db);
       // console.log(remoteRsp);
       // console.log(local);
       // console.log(localHistory);
 
-      const mixedStates = ensembleMixedStates(
+      const mixedStates = await ensembleMixedStates(
         remoteRsp.Contents,
         local,
-        localHistory
+        localHistory,
+        this.db
       );
 
       for (const [key, val] of Object.entries(mixedStates)) {
@@ -100,7 +101,7 @@ export default class SaveRemotePlugin extends Plugin {
 
       new Notice("Save Remote Sync data exchanging!");
 
-      doActualSync(
+      await doActualSync(
         s3Client,
         this.settings.s3,
         this.db,
@@ -130,7 +131,7 @@ export default class SaveRemotePlugin extends Plugin {
 
   onunload() {
     console.log("unloading plugin obsidian-save-remote");
-    this.destroyDB();
+    this.destroyDBs();
   }
 
   async loadSettings() {
@@ -142,11 +143,11 @@ export default class SaveRemotePlugin extends Plugin {
   }
 
   async prepareDB() {
-    this.db = await prepareDB();
+    this.db = await prepareDBs();
   }
 
-  destroyDB() {
-    destroyDB(this.db);
+  destroyDBs() {
+    destroyDBs(this.db);
   }
 }
 
diff --git a/src/misc.ts b/src/misc.ts
index 1aa11b1..fa795b6 100644
--- a/src/misc.ts
+++ b/src/misc.ts
@@ -1,6 +1,8 @@
 import { Vault } from "obsidian";
 import * as path from "path";
 
+export type SUPPORTED_SERVICES_TYPE = "s3" | "webdav" | "ftp";
+
 export const ignoreHiddenFiles = (item: string) => {
   const basename = path.basename(item);
   return basename === "." || basename[0] !== ".";
diff --git a/src/s3.ts b/src/s3.ts
index 7e3997d..246ad1e 100644
--- a/src/s3.ts
+++ b/src/s3.ts
@@ -9,6 +9,7 @@ import {
   PutObjectCommand,
   GetObjectCommand,
   DeleteObjectCommand,
+  HeadObjectCommand,
 } from "@aws-sdk/client-s3";
 
 import type { _Object } from "@aws-sdk/client-s3";
@@ -46,6 +47,19 @@ export const getS3Client = (s3Config: S3Config) => {
   return s3Client;
 };
 
+export const getRemoteMeta = async (
+  s3Client: S3Client,
+  s3Config: S3Config,
+  fileOrFolderPath: string
+) => {
+  return await s3Client.send(
+    new HeadObjectCommand({
+      Bucket: s3Config.s3BucketName,
+      Key: fileOrFolderPath,
+    })
+  );
+};
+
 export const uploadToRemote = async (
   s3Client: S3Client,
   s3Config: S3Config,
@@ -62,7 +76,7 @@ export const uploadToRemote = async (
   } else if (isFolder && !isRecursively) {
     // folder
     const contentType = DEFAULT_CONTENT_TYPE;
-    return await s3Client.send(
+    await s3Client.send(
       new PutObjectCommand({
         Bucket: s3Config.s3BucketName,
         Key: fileOrFolderPath,
@@ -70,6 +84,7 @@ export const uploadToRemote = async (
         ContentType: contentType,
       })
     );
+    return await getRemoteMeta(s3Client, s3Config, fileOrFolderPath);
   } else {
     // file
     // we ignore isRecursively parameter here
@@ -78,7 +93,7 @@ export const uploadToRemote = async (
       DEFAULT_CONTENT_TYPE;
     const content = await vault.adapter.readBinary(fileOrFolderPath);
     const body = Buffer.from(content);
-    return await s3Client.send(
+    await s3Client.send(
       new PutObjectCommand({
         Bucket: s3Config.s3BucketName,
         Key: fileOrFolderPath,
@@ -86,6 +101,7 @@ export const uploadToRemote = async (
         ContentType: contentType,
       })
     );
+    return await getRemoteMeta(s3Client, s3Config, fileOrFolderPath);
   }
 };
 
diff --git a/src/sync.ts b/src/sync.ts
index 4d168ba..3a30d5f 100644
--- a/src/sync.ts
+++ b/src/sync.ts
@@ -1,10 +1,21 @@
 import { TAbstractFile, TFolder, TFile, Vault } from "obsidian";
+
 import { S3Client } from "@aws-sdk/client-s3";
 import * as lf from "lovefield-ts/dist/es6/lf.js";
 
-import { clearHistoryOfKey, FileFolderHistoryRecord } from "./localdb";
-import { S3Config, S3ObjectType, uploadToRemote, deleteFromRemote } from "./s3";
-import { downloadFromRemote } from "./s3";
+import {
+  clearDeleteRenameHistoryOfKey,
+  FileFolderHistoryRecord,
+  upsertSyncMetaMappingDataS3,
+  getSyncMetaMappingByRemoteKeyS3,
+} from "./localdb";
+import {
+  S3Config,
+  S3ObjectType,
+  uploadToRemote,
+  deleteFromRemote,
+  downloadFromRemote,
+} from "./s3";
 import { mkdirpInVault } from "./misc";
 
 type DecisionType =
@@ -32,24 +43,43 @@ interface FileOrFolderMixedState {
   size_remote?: number;
   decision?: DecisionType;
   syncDone?: "done";
+  decision_branch?: number;
 }
 
-export const ensembleMixedStates = (
+export const ensembleMixedStates = async (
   remote: S3ObjectType[],
   local: TAbstractFile[],
-  deleteHistory: FileFolderHistoryRecord[]
+  deleteHistory: FileFolderHistoryRecord[],
+  db: lf.DatabaseConnection
 ) => {
   const results = {} as Record<string, FileOrFolderMixedState>;
 
-  remote.forEach((entry) => {
+  for (const entry of remote) {
+    const backwardMapping = await getSyncMetaMappingByRemoteKeyS3(
+      db,
+      entry.Key,
+      entry.LastModified.valueOf(),
+      entry.ETag
+    );
+
+    let key = entry.Key;
     let r = {} as FileOrFolderMixedState;
-    const key = entry.Key;
-    r = {
-      key: key,
-      exist_remote: true,
-      mtime_remote: entry.LastModified.valueOf(),
-      size_remote: entry.Size,
-    };
+    if (backwardMapping !== undefined) {
+      key = backwardMapping.local_key;
+      r = {
+        key: key,
+        exist_remote: true,
+        mtime_remote: backwardMapping.local_mtime,
+        size_remote: backwardMapping.local_size,
+      };
+    } else {
+      r = {
+        key: key,
+        exist_remote: true,
+        mtime_remote: entry.LastModified.valueOf(),
+        size_remote: entry.Size,
+      };
+    }
     if (results.hasOwnProperty(key)) {
       results[key].key = r.key;
       results[key].exist_remote = r.exist_remote;
@@ -58,15 +88,15 @@ export const ensembleMixedStates = (
     } else {
       results[key] = r;
     }
-  });
+  }
 
-  local.forEach((entry) => {
+  for (const entry of local) {
     let r = {} as FileOrFolderMixedState;
     let key = entry.path;
 
     if (entry.path === "/") {
       // ignore
-      return;
+      continue;
     } else if (entry instanceof TFile) {
       r = {
         key: entry.path,
@@ -94,9 +124,9 @@ export const ensembleMixedStates = (
     } else {
       results[key] = r;
     }
-  });
+  }
 
-  deleteHistory.forEach((entry) => {
+  for (const entry of deleteHistory) {
     let key = entry.key;
     if (entry.key_type === "folder") {
       if (!entry.key.endsWith("/")) {
@@ -119,7 +149,7 @@ export const ensembleMixedStates = (
     } else {
       results[key] = r;
     }
-  });
+  }
 
   return results;
 };
@@ -158,6 +188,7 @@ export const getOperation = (
     r.mtime_remote > r.mtime_local
   ) {
     r.decision = "download_clearhist";
+    r.decision_branch = 1;
   } else if (
     r.exist_remote &&
     r.exist_local &&
@@ -166,6 +197,7 @@ export const getOperation = (
     r.mtime_remote < r.mtime_local
   ) {
     r.decision = "upload_clearhist";
+    r.decision_branch = 2;
   } else if (
     r.exist_remote &&
     r.exist_local &&
@@ -175,26 +207,24 @@ export const getOperation = (
     r.size_local === r.size_remote
   ) {
     r.decision = "skip";
+    r.decision_branch = 3;
   } else if (
     r.exist_remote &&
     r.exist_local &&
     r.mtime_remote !== undefined &&
     r.mtime_local !== undefined &&
     r.mtime_remote === r.mtime_local &&
-    r.size_local === r.size_remote
+    r.size_local !== r.size_remote
   ) {
     r.decision = "upload_clearhist";
-  } else if (
-    r.exist_remote &&
-    r.exist_local &&
-    r.mtime_remote !== undefined &&
-    r.mtime_local === undefined
-  ) {
+    r.decision_branch = 4;
+  } else if (r.exist_remote && r.exist_local && r.mtime_local === undefined) {
     // this must be a folder!
     if (!r.key.endsWith("/")) {
       throw Error(`${r.key} is not a folder but lacks local mtime`);
     }
     r.decision = "skip";
+    r.decision_branch = 5;
   } else if (
     r.exist_remote &&
     !r.exist_local &&
@@ -204,6 +234,7 @@ export const getOperation = (
     r.mtime_remote >= r.delete_time_local
   ) {
     r.decision = "download_clearhist";
+    r.decision_branch = 6;
   } else if (
     r.exist_remote &&
     !r.exist_local &&
@@ -213,6 +244,7 @@ export const getOperation = (
     r.mtime_remote < r.delete_time_local
   ) {
     r.decision = "delremote_clearhist";
+    r.decision_branch = 7;
   } else if (
     r.exist_remote &&
     !r.exist_local &&
@@ -221,8 +253,10 @@ export const getOperation = (
     r.delete_time_local == undefined
   ) {
     r.decision = "download";
+    r.decision_branch = 8;
   } else if (!r.exist_remote && r.exist_local && r.mtime_remote === undefined) {
     r.decision = "upload_clearhist";
+    r.decision_branch = 9;
   } else if (
     !r.exist_remote &&
     !r.exist_local &&
@@ -230,6 +264,7 @@ export const getOperation = (
     r.mtime_local === undefined
   ) {
     r.decision = "clearhist";
+    r.decision_branch = 10;
   }
 
   return r;
@@ -264,10 +299,26 @@ export const doActualSync = async (
           vault,
           state.mtime_remote
         );
-        await clearHistoryOfKey(db, state.key);
+        await clearDeleteRenameHistoryOfKey(db, state.key);
       } else if (state.decision === "upload_clearhist") {
-        await uploadToRemote(s3Client, s3Config, state.key, vault, false);
-        await clearHistoryOfKey(db, state.key);
+        const remoteObjMeta = await uploadToRemote(
+          s3Client,
+          s3Config,
+          state.key,
+          vault,
+          false
+        );
+        await upsertSyncMetaMappingDataS3(
+          db,
+          state.key,
+          state.mtime_local,
+          state.size_local,
+          state.key,
+          remoteObjMeta.LastModified.valueOf(),
+          remoteObjMeta.ContentLength,
+          remoteObjMeta.ETag
+        );
+        await clearDeleteRenameHistoryOfKey(db, state.key);
       } else if (state.decision === "download") {
         await mkdirpInVault(state.key, vault);
         await downloadFromRemote(
@@ -279,11 +330,27 @@ export const doActualSync = async (
         );
       } else if (state.decision === "delremote_clearhist") {
         await deleteFromRemote(s3Client, s3Config, state.key);
-        await clearHistoryOfKey(db, state.key);
+        await clearDeleteRenameHistoryOfKey(db, state.key);
       } else if (state.decision === "upload") {
-        await uploadToRemote(s3Client, s3Config, state.key, vault, false);
+        const remoteObjMeta = await uploadToRemote(
+          s3Client,
+          s3Config,
+          state.key,
+          vault,
+          false
+        );
+        await upsertSyncMetaMappingDataS3(
+          db,
+          state.key,
+          state.mtime_local,
+          state.size_local,
+          state.key,
+          remoteObjMeta.LastModified.valueOf(),
+          remoteObjMeta.ContentLength,
+          remoteObjMeta.ETag
+        );
       } else if (state.decision === "clearhist") {
-        await clearHistoryOfKey(db, state.key);
+        await clearDeleteRenameHistoryOfKey(db, state.key);
       } else {
         throw Error("this should never happen!");
       }